Dell Venue's Screen goes blank after I answer a call or make one?

Every time I answer my phone or make a phone call, the screen goes blank and never comes back!!! I order to hang up the phone, I have to wait for the other person to hang up, or I have to take the battery out, it is so frustrating.  I have tried touching the screen, pushing the back, home and menu buttons, and I have pushed the power button quickly and held it down and nothing works and I tired of having a phone i can only text message on!! Someone please help me