I call a few times, and if I am given a different excuse each time, I realize that I am wasting my time and effort on them.
It may sound as though I should follow it up, and this is true I know, but I would just get seriously stressed, angry, and more disturbingly perhaps, inclined to do something stupid in retaliation.
But two wrongs don't make a right, so I cull them there and then and concentrate on looking after the decent customers I have who appreciate my service. I have several good friends who are also window cleaners in my town, so I forewarn them to avoid those who have stung me. Their chances of getting another decent window cleaner range from slim to impossible.
John