I'm sorry to hear about your touchscreen issues, and I'd like to look further into this. Could you private message me with the 15-digit IMEI number of your phone (found under where the battery sits.) This will let me find out more about the phone and verify warranty, if needed.
Also, if you are ok with clearing out your phone of everything except for your Gmail backup, paid apps, SIM card and SD card, I have had success with a hard button master reset;
I hope this helps
Same thing happened to me, but Tmobile wasn't willing to compesate me for the piece of junk. They just wanted to sell me a newer much more expensive replacement since it stopped working half way through my 2 year contract. Not to happy with them. Should have gone directly to AT&T, which has much better reception. No more Samsung touch phones for me!!!!