I had that problem. I read and researched a LOT. I changed my screen, it worked for a bit, then not. I tried the twisting phone thing (BAD IDEA) and finally learned about the IC touch chip, which is located under the logic board.
I found a video and decided to try it, and it worked!!
I had touch issues but not the gray lines up top.
It turns since the logic board and case of the phone are bendable, the IC chip gets "unsold", it lifts and doesn´t make a connection, therefore no touch.
I removed the logic board very carefully,(in the picture the touch IC chip is the acqua colored one,)I made a tin foil square same size as the chip and placed it on top. I heated a micro soldering iron, and used only the screw on the side that heats up, and placed it on top of the tin foil square, 3 intervals of 30 seconds, then pushed it down gently. Then made another square of mechanical tape and placed it on top to create pressure and to make sure the chip stays in place, and covered it back again with the original tape cover.
Replaced the logic board and voila, it´s been working for 3 weeks now with no problems, not once has the touch failed.
One thing though, afterwards the flash and volume button not working. Can´t tell if didn´t work before since I was not able to test anything since I couldn´t even unblock the phone or use it at all whatsoever.
I´m currently looking for a solution to those issues. Since it´s not a deadly issue, and I´m still able to turn the volume up and down with the control center, I still use my phone this way.
The no flash and no flashlight thing is kind of a pain, though. When I try to turn on the flashlight or take a picture using the flash it flickers very lightly for a second, then nothing.
If anyone has any ideas....