The practice my T and Pdoc are at ask for credit/debit card info in the initial start up paperwork. So if you miss a payment, they charge your card automatically. If you don't give that info then they will bill you. I had an issue with my card once and I called their billing department and she let me pay in 3 payments, over 2 weeks. but that was as flexible as it got. I've read reviews online and there are some scathing ones about this policy and that do say receptionists won't schedule appointments for you if you owe any money. The providers try to stay pretty from any financial dealings. My instinct would be to cancel if I knew I couldn't afford it.