Defy is bad products

I'm complaining about defy. I bought a defy microwave at game kenilworth. The microwave heats the food then sometimes it does not heat the food. I took the microwave back to game and they sent it to defy. Defy came back and said they can't refund or replace the microwave because they say they can't find the problem. Defy if you looking at this I need you to refund me for the microwave please. The microwave is not even 6 months old.