Screen not working, after being dropped.

I dropped my phone one night, the floor was very hard, like cement. i picked up my phone, clicked the home button, no cracks, nothing happened to my screen but when i go to unlock it it didn't slide, i tried again and again it wouldn't work. i reset my phone and tried again, still wouldn't work. texts messages, phone calls, and notifications come through but i can't unlock my phone to reply or answer my calls or anything. i took it to some people who fixes screens and they replaced my screen with 3 different screens and each was brand new screens, neither of them worked. They couldn't even find a solution to what is wrong with my phone. i rarely drop my phone and I've only had it for a year, so it's still fairly new. Can anybody help me with my problem?