Problem with screen on samsung D600

My missus has got a samsung D600,and the screen has stopped working correctly,it has gradually got worse
The best way i can describe it,is that there is a "wave" that goes from top to bottom,and the graphics are slighty distorted
the actual background of the screen stays put,i.e if a photo is used as a background,it doesnt alter its position

anyone any ideas what causes this?
I guess the phone is fooked,and is due to be replaced now i guess