WiFi Calling Test
To ensure that devices using WiFi calling do not switch between WiFi and cellular service during an active call, you can perform the following steps:
Activate Airplane Mode on your phone.
Initiate a call to test the call quality while your phone is in Airplane Mode.
By following these steps, you can assess the call quality and verify that the phone remains connected to WiFi for the duration of the call, without any interference from cellular service.