We went thru the same thing with them. They couldn't uderstand the concept, or chose to play dumb on it.  We had been doing their work for almost 10 years, no matter what interval they are paying on we should get a check every month whether it is 30, 60, 90 or 120 days! We would do the same thing, shut them down until we received checks only to receive partials. We told them that we would not do anything for them until their slate was 100% clean! Here we are 6 months later and they still owe us another $300.00. At this point, even with full payment achieved we would not get involved with them again!

We made it clear in the county that they were a serious risk for payment and that they owed us money from more than 6 months ago, but someone is always foolish enough to do their work anyway in spite of the warnings!