So every time I make a call, the phone screen goes black. The only way to get it back is to make it think I'm going to shut it down by holding the power button. I then scroll up and I get three seconds of seeing the data for the call... If a call is made I can't end the call... I'm getting frustrated with this as I've spent hours getting this phone set how I want...
You cannot hold the phone up to your ear or tap the screen? If not, sounds like a proximity sensor and you might need to return this phone and exchange.
Had the same problem yesterday. Bought 2 Lumia 735 phones with glass screen protectors. One was able to make calls with the screen showing and the other would go black. Had to keep pressing the on-off button to view the call screen. I did to factory resets to no avail. Had the phone replaced at the Verizon store including a new glass screen protector. Still didn't work. We removed the glass screen protector and the phone worked flawlessly.
Hope this helped!
Fortunately that Gorilla Glass 3 used on the Lumia 735 screen is tough stuff. Lumia phones are some of the only phones I'd use without a tempered glass screen protector.