Make sure that you define your terms, and you set expectations. AAll too often, projects are delayed because someone somewhere isn't clear on terms,, expectations, or delivery. That's how you end up in an overrun of time, resources, money, or all of the above.
That said, if someone on the team has been informed of these things repeatedly and is still off the reservation, then the problem is not you. Hold to your agreement, which you hopefully got in writing.
If they insist, despite proof to the contrary, that you are in the wrong, then you must decide if it's ok to fire a customer.
(Hint: It's totally ok to fire a customer)