I have problems making WiFi calls on my Sony Xperia 1

Press the phone icon.

Press the menu icon.

Press Settings.

Press Calling accounts.

Press the name of the SIM.

Press Wi-Fi calling.

Press the indicator to turn the function on or off.

Press the Home key to return to the home screen.

Slide two fingers downwards starting from the top of the screen.

Press the settings icon.

Press System.

Press Advanced.

Press Software update. If a new software version is available, it's displayed. Follow the instructions on the screen to update the phone software.

Press and hold On/Off.

Simultaneously, press and hold the upper part of the Volume key and keep them both pressed until your phone restarts.