It's wrong to withhold payment to someone for services rendered.
Bob thought there was a leaky pipe in his basement so he hired a plumber who didn't find anything wrong with the pipes.
Bob wants to conclude his business with the plumber.
Bob reimburses the plumber for the inspection and hires him to find out the actual cause of the problem.
Bob refuses to pay the plumber since he didn't perform any repairs.
The plumber discovers a leaky water main just outside Bob's foundation, and Bob sues the city.
The plumber, having done the job Bob asked him to perform, sues Bob for breach of contract.