Our oven has been playing up, didnt get hot at lunchtime. Tried again but no luck. Called out company that advertises "no call out charge guaranteed" on website. Guy comes out, plays with oven for 5 mins, says there is nothing wrong with oven and I must have just been unlucky earlier 
And then he hands me a bill for £48 for "labour" ... AIBU to refuse to pay this as it says no call out charge?