screen goes blank

[Electrode]

Iv had my phone 4 about 3 weeks and not all the time but often. When I make a call and hit send, the screen goes dark, as if it times out or something. I'm wanting to put it on speaker phone, that where the problem. Only sunre way iv found to get display. Back on first try is to slide keybord open.
Any tbougbhts ?

 

[ConqSoft]

Are you using any cases or screen protectors, or holding your hands on the phone in a way that would block the proximity sensors?

 

[Electrode]

I have a verizon screen protector. And I usally hold it flat looking down at it, but in a portate position. Where might these snsors. Be?