I've had my phone since last August and all of a sudden when I'm on a telephone call and a take the phone from my ear, the telephone screen has disappeared and I have to pull down the banner manually to either end the call or anything else on the phone screen. This happens even after a couple of seconds. I have went to the settings and changed the display to two minutes and this doesn't work either. Does anyone know what causes this or how to switch back? Any help would be appreciated.