Sony Xperia 5 III
Android 11.0
1 Find "Call forwarding"
Press the phone icon.
Press the menu icon.
Press Settings.
Press Calling accounts.
Press the name of the SIM.
Press Call forwarding.
2 Divert calls to voicemail
Press the required divert type.
Key in +447836121121 and press TURN ON.
+447836121121
3 Return to the home screen
Press the Home key to return to the home screen.