Here is my story.

My current house has an additional switch on the first floor to control the furnace in basemet. One day I found the furnace did not run, and could not figure out why. So I had to call a heating technician. Once he arrived, he pointed out that the switch on the first floor was off. Regardless of the fact that no additional work was done, I still paid $99 he charged.

Since I called and he made the trip, I had the obligation to pay him the initial charge of $99.00.