Re: Scree Display Issue
The proximity sensor might be obscured by something. Make sure the area is clean (the sensor is near the front-facing camera). If you have a screen protector, consider removing it. If you have a case that doesn't fit very well, make sure it doesn't hang over that area.
I recall that certain Samsung devices had a proximity sensor that was actually recessed, thus making it easier for bits of lint or dust to clog it up, and thus constantly trigger the sensor while on a call. If the Note 4's sensor is like that, make sure the area is clear of debris.