I would say most of the window cleaners in the area have received the same message at one time or
another in other words you wont have been the first.
Iv had a few over the years but never get too annoyed, at the most you only lose a few extra minutes of work time.
I'm not a great fan of charging extra on first cleans when trying to build a round, I just think at times it can give the
wrong impression.
If a customer recommends me to a friend or neighbour(which most do) then that covers the extra cost for me.
Different when your round is full and you don't care if you get the custom or not.