Poor customer service

Iv have my hisence tv for almost 4 years and it really has been qualifty , it has now a problem where the picture will go blank and the sound will keep playing It has a 4 year warranty so it's still is under warranty, hisence has claimed that they cannot replace it but only repair I am not expert in electronics but its seems the LED light is worn out and I foresee this issue re occurring and u feel hisence wants do to a short term fix and not lose on replacing the tv