theres not a lot you can do really.
When they say to me "can you leave me out this time?"
I sometimes say "ok, ill cross you off the books"
Customer: "oh no, i just mean this time"
me: "well the thing is, i only really have regular customers. I make sure i clean your windows regularly, so i need regular customers. I mean, i still have to pay my mortgage no matter what the weather is like. ..... So would you like me to clean them, today?"
They usually say yes then, but still some dont.
I dont like cleaning in the rain anyway!