Hope this will make you laugh:
When I was WC'ing last time (about 5 years ago) my fiance worked with me for a few months.
Part of my round was an entire close of about 20 houses, but after cleaning one of the houses the neighbour complained as the back door was messy (just a fussy customer). But I apologised, promised it wouldn't happen again, cleaned it again...problem solved. But no! The customer asked me not to do the windows again...
About a year later, I am now working on my own and the above mentioned customer came out to me and I thought "they are going to ask me to clean their windows again, as I do the whole street and they can't get another WC." The chap came over to me and said:
"Hi mate, I wondered if you could clean my windows again as the other chap who used to work with you was probably the one who made the back door messy and now he's not with you I'm sure you will do a better job"
I was grinning inside as I replied to him:
"Well. that 'chap' that was with me last time is now my wife and I know she did an excellent job..and no, I would not like to clean your windows"
You should have seen the look on his face when he realised he had just insulted me and my wife!!
Sometime you are just better of without some customers...