Samsung S3 Touch not responding!

[Abid Ali1]

I got samsung s3 3 days ago and I noticed a problem. Sometime the touch screen stop responding while the physical buttons(lock, home and volume) works fine. In this situation when I lock and unlock the phone by that lock button the touch starts responding and then works fine. I applied Water-live-paper on the screen the I noticed that when the screen stuck the water look like it has been touch continuously at a single point and that's why the screen stops responding!.......... so to make a conclusion sometime the screen is continuously torched by itself so when I touch it its not responding I have to lock and unlock the phone get out of this frustrating moment!
I hope I have provided enough details about my problem, plz recommended me what should I do now! this phone is sent by my brother form abroad,,, I am very frustrated. plz help!