electric oven diplomat aba3340?

I bought this oven in June 08 and it is faulty but i have just been told that my warranty is void due to the collapse of mfi and the extended warranty which i purchased is also void!
Lately when i switch my oven on my grill also comes on which means most of my food ends up burnt or not cooked properly. This cooker has a settings for grill, large grill, top heat (oven), bottom heat (oven) and top and bottom heat (oven) with fan. The only way I can cook without my grill coming on is through the bottom heat which means it takes ages to cook anything!! Does anyone no what is wrong with my oven??