No, but i had one WC do one of my houses the day before i went to do it..
Because the husband was at home he just paid him.. :
His wife went berserk at him, and said dont pay anyone..
The WC turned up the following month were she told him he wasn't required. I missed out on one clean but at least she is loyal!
Id just make sure you tell all your customers the deal, a letter or phone call to advise that there is a dodgy guy going round telling lies to get the job, so unless they hear from you saying otherwise you are fully committed to ensuring they have a reliable window cleaner.