iPhone 6S Screen replacement, Touch working. No display

Hi everyone. So the inevitable happened. I dropped my phone and smashed the screen. The digitizer and LCD were both smashed. I have repaired phone screens before and I just wasn't up to replacing this one. So I just got a company to do it for me. They done it well and the phone was working perfectly. I noticed however that there was some problems with the screen. 3D touch wasn't working as it should and there was a strange white haze over the screen when the proximity sensor was activated during a phone call. So i took it back to them and they replaced the screen. I went to pick it up and test it out. I was trying to recreate the problem with the phone call and when I activated the proximity sensor the phone just stopped working. I left it with them and the guy said that he put 6 other screens on it and it was working for a second then it just didn't work anymore. He handed it back to me. The phone is still working. I am able to accept calls and use the touch screen but the LCD isn't working. I have checked to see if its a backlight issue and its not. Any body have a clue what the problem could be.

Thanks.

Ross.