SAMSUNG SMG781B Smartphone SAMSUNG SMG781B Smartphone product


Dual Messenger
Install the second app and use two separate accounts for the same messenger app.

  1. On the Settings screen, tap Advanced features → Dual Messenger.
    Supported apps will appear.
  2. Tap the switch of an app to install the second app.
    The second app will be installed. The second app’s icon will be displayed with SAMSUNG SMG781B Smartphone fig 1 When you receive notifications from the second app, the notifications will be displayed withSAMSUNG SMG781B Smartphone fig 2 to distinguish them from the first app’s notifications. SAMSUNG SMG781B Smartphone fig 3


  • The Dual Messenger feature may not be available depending on the app.
  • Some features of the app may be limited for the second app.

Uninstalling a second app

  1. On the Settings screen, tap Advanced features → Dual Messenger.
  2. Tap the switch of the app you want to uninstall and tap Disable or Uninstall.
    All data related to the second app will be deleted.

Note: If you uninstall the first app, the second app will also be deleted.

Digital Wellbeing and parental controls


View the history of your device usage and use features to prevent your device from interfering with your life. You can also set up parental controls for your children and manage their digital use.
On the Settings screen, tap Digital Wellbeing and parental controls.

  • Digital Wellbeing: View the daily usage history of your device. Refer to Digital Wellbeing for more information.
  • Parental controls: Manage your children’s digital use.

Digital Wellbeing

View the daily usage history of your device. You can also limit usage time or change the notification settings for each app.
On the Settings screen, tap Digital Wellbeing and parental controls → Digital Wellbeing. SAMSUNG SMG781B Smartphone fig 4

Setting timers for apps

You can limit the daily usage time for each app by setting a timer. When you reach the limit, the app will be deactivated and you cannot use it.

  1. On the Settings screen, tap Digital Wellbeing and parental controls → App timers.
  2. Tap No timer next to the app you want and set the time.

Activating wind-down mode
You can activate wind-down mode to reduce eye strain before sleeping and prevent your sleep from being disturbed.

  1. On the Settings screen, tap Digital Wellbeing and parental controls → Wind Down → Start now.
  2. To set the schedule to activate wind-down mode, tap Set a schedule, tap the switch to activate it, and then set the days and time.

Device care

The device care feature provides an overview of the status of your device’s battery, storage, memory, and system security. You can also automatically optimise the device with a tap of your finger. SAMSUNG SMG781B Smartphone fig 5

Optimising your device

On the Settings screen, tap Device care → Optimise now.
The quick optimisation feature improves device performance through the following actions.

  • Clearing some memory.
  • Deleting unnecessary files and closing apps running in the background.
  • Managing abnormal battery usage.
  • Scanning for crashed apps and malware.

Using the auto-optimization feature

You can set the device to perform auto optimisation when your device is not in use. Tap → Advanced → Auto optimization and tap the switch to activate it. If you want to set the time to perform auto-optimization, tap Time.


Check the remaining battery power and time to use the device. For devices with low battery levels, conserve battery power by activating power saving features.
On the Settings screen, tap Device care → Battery. 

  • The usage time left shows the time remaining before the battery power runs out. Usage time left may vary depending on your device settings and operating conditions.
  • You may not receive notifications from some apps that use power saving mode.

Power mode
Select a power mode that suits your device usage purposes. Tap Power mode and select an option.

  • Optimized: Optimised for a balance between the device’s performance and battery usage.
  • Medium power saving: Activate power-saving mode to extend the battery’s usage time.
  • Maximum power saving: In maximum power saving mode, the device decreases battery consumption by activating dark mode and limiting the apps and features available. Network connections, except for the mobile network, will be deactivated.

You can set the device to charge the battery more quickly. Tap the Fast cable charging switch to activate it.

Adaptive power saving

You can set the device to activate power saving mode automatically based on your usage patterns and the remaining battery power.
Tap Power mode and tap the Adaptive power saving switch to activate it. Your device will activate power saving mode based on the situation to extend the battery’s usage time.

Managing battery usage for each app

You can save battery power by preventing apps that are running in the background from using battery power when they are not being used. Tap Battery usage, select apps from the apps list, and then tap the Put app to sleep switch to activate the feature.


Check the status of the used and available memory. On the Settings screen, tap Device care → Storage. 

  • The actual available capacity of the internal memory is less than the specified capacity because the operating system and default apps occupy part of the memory. The available capacity may change when you update the device.
  • You can view the available capacity of the internal memory in the Specification section for your device on the Samsung website.

Managing the memory

To delete residual files, such as cache, tap Clean now. To delete files or uninstall apps that you do not use any more, select a category. Then, tick items to select and tap Delete.

On the Settings screen, tap Device care → Memory.
To speed up your device by stopping apps running in the background, tick apps from the apps list, and tap Clean now.

Check the device’s security status. This feature scans your device for malware.
On the Settings screen, tap Device care → Security → Scan phone. 


Manage the device’s apps and change their settings. You can view the apps’ usage information, change their notification or permission settings, or uninstall or disable unnecessary apps.
On the Settings screen, tap Apps.

General management

Customize your device’s system settings or reset the device.
On the Settings screen, tap General management. 

  • Language and input: Select device languages and change settings, such as keyboards and voice input types. Some options may not be available depending on the selected language. Refer to Adding device languages for more information.
  • Date and time: Access and alter the settings to control how the device displays the time and date.
    Note: If the battery remains fully discharged, the time and date is reset.
  • Contact us: Ask questions or view frequently asked questions.
  • Reset: Reset your device’s settings or perform a factory data reset. You can reset all your settings, or only network settings, or accessibility settings. You can also set the device to restart at a preset time for device optimisation.

Adding device languages

You can add languages to use on your device.

  1. On the Settings screen, tap General management → Language and input → Language Add language.
    To view all the languages that can be added, tap → All languages. 
  2. Select a language to add.
  3. To set the selected language as the default language, tap Set as default. To keep the current language setting, tap Keep current.
    The selected language will be added to your languages list. If you changed the default language, the selected language will be added to the top of the list.

To change the default language from your languages list, select the language you want and tap Apply. If an app does not support the default language, the next supported language in the list will be used.


Configure various settings to improve accessibility to the device.
On the Settings screen, tap Accessibility.

  • Screen reader: Activate Voice Assistant, which provides voice feedback. To view help information to learn how to use this feature, tap Tutorial.
  • Visibility enhancements: Customise the settings to improve accessibility for visually impaired users.
  • Hearing enhancements: Customise the settings to improve accessibility for users with hearing impairment.
  • Interaction and dexterity: Customise the settings to improve accessibility for users who have reduced dexterity.
  • Advanced settings: Configure settings for Direct access and notification features.
  • Installed services: View accessibility services installed on the device.
  • About Accessibility: View the Accessibility information.
  • Contact us: Ask questions or view frequently asked questions.

Software update

Update your device’s software via the firmware over-the-air (FOTA) service. You can also schedule software updates.
On the Settings screen, tap Software update.
NOTE: If emergency software updates are released for your device’s security and to block new types of security threats, they will be installed automatically without your agreement.

  • Download and install: Check for and install updates manually.
  • Auto download over Wi-Fi: Set the device to download updates automatically when connected to a Wi-Fi network.
  • Last update: View information about the last software update.

Security updates information

Security updates are provided to strengthen the security of your device and protect your personal information. For security updates for your model, visit 
NOTE: The website supports only some languages.

About phone

Access your device’s information.
On the Settings screen, tap About phone. To change your device’s name, tap Edit.

  • Status: View various device information, such as the SIM card status, Wi-Fi MAC address, and serial number.
  • Legal information: View legal information related to the device, such as safety information and the open source licence.
  • Software information: View the device’s software information, such as its operating system version and firmware version.
  • Battery information: View the device’s battery status and information.



Before contacting a Samsung Service Centre, please attempt the following solutions. Some situations may not apply to your device.
When you turn on your device or while you are using the device, it prompts you to enter one of the following codes:

  • Password: When the device lock feature is enabled, you must enter the password you set for the device.
  • PIN: When using the device for the first time or when the PIN requirement is enabled, you must enter the PIN supplied with the SIM or USIM card. You can disable this feature by using the Lock SIM card menu.
  • PUK: Your SIM or USIM card is blocked, usually as a result of entering your PIN incorrectly several times. You must enter the PUK supplied by your service provider.
  • PIN2: When you access a menu requiring the PIN2, you must enter the PIN2 supplied with the SIM or USIM card. For more information, contact your service provider.

Your device displays network or service error messages 

  • When you are in areas with weak signals or poor reception, you may lose reception. Move to another area and try again. While moving, error messages may appear repeatedly.
  •  You cannot access some options without a subscription. For more information, contact your service provider.

Your device does not turn on
When the battery is completely discharged, your device will not turn on. Fully charge the battery before turning on the device.

The touchscreen responds slowly or improperly 

  • If you attach a screen protector or optional accessories to the touchscreen, the touchscreen may not function properly.
  • If you are wearing gloves, if your hands are not clean while touching the touchscreen, or if you tap the screen with sharp objects or your fingertips, the touchscreen may malfunction.
  • The touchscreen may malfunction in humid conditions or when exposed to water.
  • Restart your device to clear any temporary software bugs.
  • Ensure that your device software is updated to the latest version.
  • If the touchscreen is scratched or damaged, visit a Samsung Service Centre.

Your device freezes or encounters a fatal error
Try the following solutions. If the problem is still not resolved, contact a Samsung Service Centre.

Restarting the device
If your device freezes or hangs, you may need to close apps or turn off the device and turn it on again.

Forcing restart
If your device is frozen and unresponsive, press and hold the Side key and the Volume Down key simultaneously for more than 7 seconds to restart it.

Resetting the device
If the methods above do not solve your problem, perform a factory data reset.
Launch the Settings app and tap General management → Reset → Factory data reset → Reset → Delete all. Before performing the factory data reset, remember to make backup copies of all important data stored in the device.

Calls are not connected 

  • Ensure that you have accessed the right cellular network.
  • Ensure that you have not set call barring for the phone number you are dialling.
  • Ensure that you have not set call barring for the incoming phone number.

Others cannot hear you speaking on a call 

  • Ensure that you are not covering the built-in microphone.
  • Ensure that the microphone is close to your mouth.
  • If using an earphone, ensure that it is properly connected.

Sound echoes during a call
Adjust the volume by pressing the Volume key or move to another area.

A cellular network or the Internet is often disconnected or audio quality is poor 

  • Ensure that you are not blocking the device’s internal antenna.
  • When you are in areas with weak signals or poor reception, you may lose reception. You may have connectivity problems due to issues with the service provider’s base station. Move to another area and try again.
  • When using the device while moving, wireless network services may be disabled due to issues with the service provider’s network.

The battery does not charge properly (For Samsung-approved chargers)

  • Ensure that the charger is connected properly.
  • Visit a Samsung Service Centre and have the battery replaced.

The battery depletes faster than when first purchased 

  • When you expose the device or the battery to very cold or very hot temperatures, the useful charge may be reduced.
  • Battery consumption will increase when you use certain features or apps, such as GPS, games, or the Internet.
  • The battery is consumable and the useful charge will get shorter over time.

Error messages appear when launching the camera
Your device must have sufficient available memory and battery power to operate the camera app. If you receive error messages when launching the camera, try the following:

  • Charge the battery.
  • Free some memory by transferring files to a computer or deleting files from your device.
  • Restart the device. If you are still having trouble with the camera app after trying these tips, contact a Samsung Service Centre.

Photo quality is poorer than the preview 

  • The quality of your photos may vary, depending on the surroundings and the photography techniques you use.
  • If you take photos in dark areas, at night, or indoors, image noise may occur or images may be out of focus.

Error messages appear when opening multimedia files

If you receive error messages or multimedia files do not play when you open them on your device, try the following:

  • Free some memory by transferring files to a computer or deleting files from your device.
  • Ensure that the music file is not Digital Rights Management (DRM)-protected. If the file is DRM-protected, ensure that you have the appropriate licence or key to play the file.
  • Ensure that the file formats are supported by the device. If a file format is not supported, such as DivX or AC3, install an app that supports it. To confirm the file formats that your device supports, visit
  • Your device supports photos and videos captured with the device. Photos and videos captured by other devices may not work properly.
  • Your device supports multimedia files that are authorised by your network service provider or providers of additional services. Some content circulated on the Internet, such as ringtones, videos, or wallpapers, may not work properly.

Bluetooth is not working well

If another Bluetooth device is not located or there are connection problems or performance malfunctions, try the following:

  • Ensure that the device you wish to connect with is ready to be scanned or connected to.
  • Ensure that your device and the other Bluetooth device are within the maximum Bluetooth range (10 m).
  • On your device, launch the Settings app, tap Connections, and then tap the Bluetooth switch to re-activate it.
  • On your device, launch the Settings app, tap General management → Reset → Reset network settings → Reset settings → Reset to reset network settings. You may lose registered information when performing the reset.
    If the tips above do not solve the problem, contact a Samsung Service Centre.

A connection is not established when you connect the device to a computer 

  • Ensure that the USB cable you are using is compatible with your device.
  • Ensure that you have the proper driver installed and updated on your computer.

Your device cannot find your current location
GPS signals may be obstructed in some locations, such as indoors. Set the device to use Wi-Fi or a mobile network to find your current location in these situations.

Data stored in the device has been lost
Always make backup copies of all important data stored in the device. Otherwise, you cannot restore data if it is corrupted or lost. Samsung is not responsible for the loss of data stored in the device.

A small gap appears around the outside of the device case 

  • This gap is a necessary manufacturing feature and some minor rocking or vibration of parts may occur.
  • Over time, friction between parts may cause this gap to expand slightly.

There is not enough space in the device’s storage
Delete unnecessary data, such as cache, using the device care feature or manually delete unused apps or files to free up storage space.

The Home button does not appear
The navigation bar containing the Home button may disappear while using certain apps or features. To view the navigation bar, drag upwards from the bottom of the screen.

The screen brightness adjustment bar does not appear on the notification panel
Open the notification panel by dragging the status bar downwards, and then drag the notification panel downwards. Tap → Quick panel layout and tap the Show brightness on top switch to activate it.

Removing the battery 

  • To remove the battery, contact an authorised service centre. To obtain battery removal instructions, please visit
  • For your safety, you must not attempt to remove the battery. If the battery is not properly removed, it may lead to damage to the battery and device, cause personal injury, and/or result in the device being unsafe.
  • Samsung does not accept liability for any damage or loss (whether in contract or tort, including negligence) which may arise from failure to precisely follow these warnings and instructions, other than death or personal injury caused by Samsung’s negligence.

Health and safety information

Exposure to Radio Frequency (RF) Signals
Certification Information (SAR)
Your wireless phone is a radio transmitter and receiver. It is designed and manufactured not to exceed the exposure limits for radio frequency (RF) energy set by the Federal Communications Commission (FCC) of the U.S. government. These FCC exposure limits are derived from the recommendations of two expert organizations, the National Counsel on Radiation Protection and Measurement
(NCRP) and the Institute of Electrical and Electronics Engineers (IEEE). In both cases, the recommendations were developed by scientific and engineering experts drawn from industry, government, and academia after extensive reviews of the scientific literature related to the biological effects of RF energy.
The exposure limit set by the FCC for wireless mobile phones employs a unit of measurement known as the Specific Absorption Rate (SAR). The SAR is a measure of the rate of absorption of RF energy by the human body expressed in units of watts per kilogram (W/kg). The FCC requires wireless phones to comply with a safety limit of 1.6 watts per kilogram (1.6 W/ kg). The FCC exposure limit incorporates a substantial margin of safety to give additional protection to the public and to account for any variations in measurements.
SAR tests are conducted using standard operating positions accepted by the FCC with the phone transmitting at its highest certified power level in all tested frequency bands. Although the SAR is determined at the highest certified power level, the actual SAR level of the phone while operating can be well below the maximum value. This is because the phone is designed to operate at multiple power levels so as to use only the power required to reach the network. In general, the closer you are to a wireless base station antenna, the lower the power output.
Before a new model phone is available for sale to the public, it must be tested and certified to the FCC that it does not exceed the exposure limit established by the FCC. Tests for each model phone are performed in positions and locations (e.g. at the ear and worn on the body) as required by the FCC.

For body-worn operation, this model phone has been tested and meets the FCC RF exposure guidelines when used with a Samsung accessory designated for this product or when used with an accessory that contains no metal and that positions the handset a minimum of 1.5 cm from the body.
Non-compliance with the above restrictions may result in a violation of FCC RF exposure guidelines.
SAR information on this and other model phones can be viewed online at Please use the phone FCC ID number for search, A3LSMG781B. Sometimes it may be necessary to remove the battery pack to find the number. Once you have the FCC ID number for a particular phone, follow the instructions on the website and it should provide values for typical or maximum SAR for a particular phone. Additional product specific SAR information can also be obtained at 

FCC Notice and Cautions FCC Notice 

This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions:

  1. this device may not cause harmful interference, and
  2. this device must accept any interference received, including interference that may cause undesired operation.

This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or
television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the following measures:

  • Reorient or relocate the receiving antenna.
  • Increase the separation between the equipment and receiver.
  • Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.
  • Consult the dealer or an experienced radio/TV technician for help.

The phone may cause TV or radio interference if used in close proximity to receiving equipment. The FCC can require you to stop using the phone if such interference cannot be eliminated.
Vehicles using liquefied petroleum gas (such as propane or butane) must comply with the National Fire Protection Standard (NFPA-58). For a copy of this standard contact the National Fire Protection Association, One Battery March Park, Quincy, MA 02269, Attn: Publication Sales Division.

Changes or modifications made in the radio phone, not expressly approved by Samsung, will void the user’s authority to operate the equipment. The use of any unauthorized accessories may be dangerous and void the phone warranty if said accessories cause damage or a defect to the phone. Although your phone is quite sturdy, it is a complex piece of equipment and can be broken. Avoid dropping, hitting, bending or sitting on it.

Documents / Resources

SAMSUNG SMG781B Smartphone [pdf] User Guide
SMG781B, A3LSMG781B, SMG781B Smartphone, SMG781B, Smartphone


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