I make it known up-front when called for service/repair I intend to inspect the majority of the system to determine additional problems.
I used to chase client's demands and be subject to their whimsy's. Not any longer.
If the client does not want the additional work I deem necessary to address the problem(s) I won't do any of the work. Period. No way will I be subject again to the incessant return demands to piecemeal a system back together.
The second I get interference from the client I immediately "size" them for revenue potential. Some I'll stick around and discuss the site issues with, on more than a few I simply drove away. I have left more than a few standing at the curb with their mouths open in astonishment when I said "Adios". And I have gotten some really nice, long term maintenance accounts simply because the client couldn't push me around - makes up for the difference.
Nice Try = You Suck Spelled Differently