If you are giving them a set date and are sticking to it, then, drop them, or do the front only, charge 2/3rds of the whole price.
If your not arriving on the specified day, well no one to blame but yourself.
Best solution for these is no chat with them, agree on a front only service, or ask for a key ( or one to be left, so you can lock up afterwards ) if none of this works, them let them know you will no longer be cleaning them,
Try to keep the upper hand, some will be helpful especially when they realise your prepared to be jerked around, others are just not worth keeping for the aggro.
Darran