This is NOT a solution. People can't be factory resetting their devices every other week. It takes a lot of time and effort to setup a device.
Switch off your phone with out simcard ,Switch on your phone insert your simcard, this is work for me with O2 network
And change WiFi call settings for prefer network wifi
I know because I don't go for a bypass surgery if I have a sore throat and cough. Don't suggest nonsensical solutions if you haven't actually got a real solution.
Anyway, if your wi-fi calling was working previously and stopped working after an update, here's the real solution:
1. Go into Settings>Connections> Mobile Networks. Reset APN settings to 'Default'.
2. Select Network Operator, disable 'Select Automatically', do a manual scan and select your network operator.
3. Reboot the device.
4. Put the device on flight mode, enable wi-fi and then check WiFi Calling by making a call.
It should be working now.
Once it's working, you can re-enable the 'Select Automatically' setting under Network Operators.
You just don't get it, do you? A factory reset is an unnecessarily extreme solution for a minor issue. The point is to find a solution that works without having to demolish the entire house to fix a broken window.