Share your experience!
Are you certain that there's nothing partially blocking/covering the proximity sensor?
Boot the phone in safe mode:
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008
You should take it back and let them look at it.
I experience this problem also. The diagnostics show the proximity sensor as working however whilst in a call I can feel the vibration of button presses against my cheek.
I also have this problem. Do I really have to send the phone back or has anyone found out what the problem is?
I have the same issue. I use Tempered Glass Screen Protector though? Could this have anything to do with the issue?