I once had a situation where the custie wasn't happy with the job. She didn't want me to clean for her again. I had been cleaning for her for a few years and I did them just the same way as always. She wouldn't pay me. These were my ladder and squeegee days.
In the end we agreed that she pay the money that I would normally have received to a charity. We were both happy that the other hadn't gained I think and we left it at that. She could be a bit of a PITA at times if truth be told.