A couple of years ago there was a guy that would bring his completely un-maintained road bike into the shop , (on busy saturdays of course) and complain that it was not shifting right or stopping quickly enough.
We would put the bike on the stand and spend 20 min explaining all the things that needed replaced adjusted.
Then we would give him an estimate of the time and cost.
He would say no I don't want to do all that just fix the shifting....another 20 minutes explaining chain wear and why his cog teeth look like shark fins....He would say "I don't care about that, I just want you to fix the shifting"
The shop owner would have to come over, pull his bike from the stand and walk him out back and explain that we don't have time for him today and to come back another time.
Finally, one day his chain breaks and the guy comes in for a new chain. We replace the chain, explain what is going to happen when he tries to ride (because he only wants a chain) and send him off.
He comes back the next Sat and in front of a shop full of customers starts yelling that we ruined his pride and joy.
Fast forward to today on bike forums........

Enjoy