Since I got my iPhone 12 Pro, when I am on a call randomly the screen goes black and becomes unresponsive when I touch the screen if I want to use the mute or loudspeaker or even end the call.
It randomly happens if I am on a phone call via loud speaker the screen will go to sleep, and if I tap it to wake the screen up it becomes unresponsive and I end up having to use the side button to end the call, this problem happens randomly and even if I'm not using loudspeaker. Does anyone think it's a problem with IOS 14.3 or my iPhone 12 Pro?
Reboot phone.
Reset all settings.
Reset network settings.
Erase and restore from backup.
Erase and set up as new.
If none of these steps work for you then you can pretty much narrow it down to being your hardware. I just tried to replicate your issue and it didn’t happen.