Expecting me to move around my bookings for them, when I have them.
Back when I was busier, I might have two or three bookings in one day. A client calls up and asks for a time already booked. I tell him, he asks me to move it. I say no, he says that he's a regular and probably sees me more than the client who is already booked into that time slot.
That conversation went on for longer than it ought to. And it was circular.