Well that was interesting.
I switched the box off. Checked I had no mobile signal. Checked I’d got WiFi Calling enabled. Got a strong WiFi signal. And yet I couldn’t make a call. No WiFi calling icon or whatever on my phone. So not sure what’s going on there. A bit busy at the moment to have a look and see if I’ve missed a setting somewhere. Though now wondering whether the ‘Web Protect’ option that was suggested earlier may need looking at.
Got my WiFi Calling sorted. But only after fitting a replacement SIM. Once that was fitted - it arrived the next day - and activated - took about 15 mins - I put the phone into Airplane mode. That switches off the mobile’s 2/3/4G radio. So now just working on WiFi I could make a phone call as normal - In other words not using WhatsApp, FaceTime or whatever.
Apart from the mobile signal strength display disappearing, there wasn’t any obvious sign that I was making a WiFi call. Until that is I swiped down the signal display and it said ‘BT WiFi Call’ next to the WiFi icon.
I switched Airplane mode OFF so the mobile 2/3/4G radio was active. The signal level was about 1 or 2 bars, and I made another ‘normal’ call. Judging by the quality of the call I think it was still doing the WiFi Calling thing.
It would seem that if the WiFi signal is good , and your phone is WiFi calling compatible then it’s all seamless. The call quality is far better than if you’d only relied on the mobile signal.