i had a customer like this. I cleaned his windows three times without payment.(i usually only clean twice without payment) but he ensured me would pay for it all next time.
I called back there time and time again! i mean litterally about 12 times, but with no luck. in the end i just gave up. I could even see him hide and duck by the window once!!!
I just decided to bite the bullet and accept that i had lost the money. The total for the three cleans was only £15.
In the end i was putting so much time into calling back, and it got me so annoyed when i went there and he wouldnt answer even though he was blatently in, i just stopped calling.
i tried a few different things, knocking continuosly, leaving notes, even threatening court action. Once i was with one of my mates, a big guy, and we went up to the house together, but still nothing.
sometimes, its just not worth the hastle!!