Co-miserate... Luckily such customers are rare here these days. Tell him if his mechanic rebuilt the steering & front end on his car, then months later it started having a leak out the gas tank. Or if he had his windshield replaced, then the back bumper fell off it's the mechanic's responsibilty. Problems aren't related & each takes $$$ to fix. Or give up driving, and walk everywhere.
Similar analogies with dentists, doctors, construction contractors, etc etc. Some people... think just because they threw money at their problem, that no other problems should show up, forever. IOW, whoever fixed it last, owns all problems that develop in the future. World ain't like that dear crustomers, get over it.