Purple TV

I have a hisense 55” tv that is 3.5 years old, but still under warranty. It has developed purple blotches on the screen, which really spoil the viewing experience. I reported the problem to Hisense and a technician came out. Well my tv has still got purple blotches. I reported this to Hisense again and to date have had no further response. What are you waiting for Hisense? For my warranty to run out?