There is a limit to how long the doctor's office has to bill the insurance company. If the Insurance company denies a claim for "timely filing", then it is not your fault, and you should not have to pay. First, I would call your insurance company back to find out if it was a covered service. Why did you get a bill in the first place? Was it because you hadn't met your deductible yet? Were you responsible for only a percentage of the total cost? Then, you should call and speak to a billing manager at your doctor's office, to let them know what your insurance company said. It sounds like the doctor's office doesn't really have their act together as far as billing is concerned. If the charges are duplicate, then it's obviously their fault, and you shouldn't have to pay. If they didn't bill for all or part of the procedure on time, then it's their fault, too. I have some experience with billing and doctor's offices. If you have any more questions or need any more help with this, please contact me. Good luck!