Xperia Z2 :: Screen Won't Respond During A Call

My Xperia Z2's screen work perfectly fine until I need to make a call. The second i hit the person's name on the call log, the screen becomes black, eccentially shutting off and not allowing me to turn it back on until the call has ended. The only way for me to end call is to press the power button. And if I do not have the setting on to do so, the power button still does not allow me to turn on the screen.
 
Now, I thought it was something wrong with the proximity censor (as in a Hardware fault, explained in the back story) until yesterday when i woke up and suddenly I could make a call with the screen on, but now the person on the other side was not recieving my Audio (but my phone mic was still working). After turning my phone off and back on, it reverted back to being able to make a call, but not being able to use the screen.