I have problems making WiFi Calls on my Samsung Galaxy J4+
If you can't use WiFi Calling, there may be several causes of the problem.
Press Phone.
Press the menu icon.
Press Settings.
Press the indicator next to 'Wi-Fi calling' to turn the function on or off.
Press the Home key to return to the home screen.
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Slide your finger downwards starting from the top of the screen.
Press the settings icon.
Press Software update.
Press Download updates manually. If a new software version is available, it's displayed. Follow the instructions on the screen to update the phone software.
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Press and hold On/Off.
Simultaneously, press and hold the Bottom volume key until your phone restarts.