After cooking a roast in the oven in early morning around 10 a.m I cut the oven off and was going to let the roast sit in the oven until lunch at 11 a.m. The oven continue to cook at eleven when i went to take the roast out it was burnt the oven never cut off and the heat seemed to be hotter than it should be we had to unplug the oven to get it to cool down. today we went to use the stove top so we plugged it back in and it started to heat up again. What is causing this? Where can I find Help?