The F11 Error signifies a "shorted key" issue. This occurs when a key on the keypad is identified as being held down for an extended period, leading to the F11 error being displayed and all oven operations being halted. To clear this error, you can initially try pressing the cancel key. If that does not clear it, killl power to the range at the breaker/fuse panel on your home or unplug it  for 2 full minutes then restore power. 

If it still gives you the f11 error, with the unit unplugged, use a hairdryer and blow warm air across the keypad, do not keep it in one place move the hair dryer side to side, after a minute or so stop. Plug the range back and see if that helped, if not you will need to replace the keypad/control. The part you need varies from model to model so if you want to know what part you need to order I will need your model number.

As far as who to call, just do a google search for your zipcode + appliance repair an you should get some local repair compaines in the search to call.