This just started recently, I've had the phone since Dec 3rd. Randomly during a call, the phone beeps in my ear. When I look at the screen, its the phone call screen like usually, but instead of showing the caller, its black/blank. You can still see the "add call" and "end" etc buttons, but nothing works and the call is gone. It stays that way on the screen until I hit the Home button. It seems like it may have something to do with the service, but I don't know that for sure. any ideas?