my oven will not turn off?

Hi I have a hotpoint ew85 cooker. my problem is even though my main fan oven is turned off with the knob, the element is still switched on and it gets extremly hot! the only way i can turn it off is by switching the main cooker switch to cut power to my entire cooker. When i do turn the knob the fan cuts in as normal but the temprature seems to be way over what it should be even to the point that theres a strong burning smell. Please help with fault and how to fix it . Thanks.