My boyfriends iPhone 6 touch screen not working after IOS 9.3.5 update

I'm not very sure if this question fits in this category but:

My boyfriends Iphone 6 was working fine until the IOS 9.3.5 came out. After he installed it his touch screen hasn't worked right since, we looked on many different websites including this one, and they said do a hard reset (holding the power button and home button together) we tried that but it would only work for maybe 5 minutes. We did a factory reset and now it won't work at all. What else can We do?