Lumia 735 has the screen go black every time I make a call so I can't access phone options such as end call. I just got this today and it's already giving me a headache!

[Newguy2015]

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...

[Snn5]

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.

[n8qxb]

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!

[47seijar]

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.