Xseries :: X7 - Deactivate Black Screen During Calls?

I thought that the X7 is supposed to use the proximity sensor to send the screen black during a call because it is next to your face. My phone automatically puts the screen black when I make a call, even if the phone is on the desk or held out in space. Either way, it is very rare for me to be able to convince the phone to bring the screen display back up, ( to do things like enter little things like pin codes ). I flip it around, hold it up to the lights, put it against something, take it away, press every part of the screen. Is there any way of setting the phone not to go black during a call?