1. Find "SIM card & mobile data"
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press SIM card & mobile data.
2. Turn VoLTE on or off
Press the required SIM.
Press the indicator next to "VoLTE Calls" to turn the function on or off.
3. Return to the home screen
Press the Home key to return to the home screen.