lg phone goes black when making a call and I can't hang up or turn off

I'm having the same problem with my phone (although I've had it for 1.5 years). I know it can't be my screen protector. What do you mean, as I'm wondering what I need to do?

 

I think what he meant is that the screen protector was blocking the proximity sensor. That makes it think the phone is still up against your face at which time it turns the screen off by design during a call. A case might do the same thing if it got a little askew. Try cleaning the screen good too. Hopefully the sensor itself isn't going bad.