Legal Question in Credit and Debt Law in California

If you've already paid, you don't owe them money. Send them a copy of the receipt for your payment with a letter of dispute by certified return receipt mail. Keep a copy for your records. If they have reported it on your credit report (that you can get free at http://www.annualcreditreport.com), include in your letter a demand that it be removed immediately.

I basically agree with Mr. Cohen, but have a little different take on the issue. If you signed an agreement to pay for services, which you almost certainly did when you became a patient, then they are within the limitations period to collect any unpaid charges from 2011. So if there are legitimately unpaid charges for services then you legally owe the money. The time to collect them has not expired. If you did, in fact, pay in full for all services provided, and there are no outstanding balances, then I agree with Mr. Cohen entirely.