I work as an IT consultant so I don't have to deal with any of the crap people in traditional customer roles do, but there have been a couple of customers we've agreed to mutual part ways with. Mostly due to them having unrealistic expectations.
One client expected us to basically be their 24/7 help desk, but only paid for like 20-30 hours a month. He wanted someone in their office from 8-5. He was like they can work on other stuff, but I need them to be here in case someone needs them. We were not an MSP. We didn't do help desk. The original contract was to help with a date center migration with flex hours to support after the move. We did project work with mainly senior consultants. This was a company with 1 IT guy and maybe 100 employees. As soon as the contract came up for renewal we were done.