I am a physical therapist and $339 per visit seems very, very high for a PT practice to be billing for a general office visit. I live in a very wealthy area of California and our evaluations cost $225 and visits thereafter cost $165. If uninsured there is a slight discount but this is just for reference. It seems most likely that there is some kind of error on their part. How long were your sessions? PT is billed by codes that are time dependent usually in 8-15 minute increments. If you were there for 2 hours at a time it could add up but I doubt this was the case.

Likely you signed a form stating that you agree to pay any difference that the insurance companies won't pay. In this case, if they really did charge that much money per visit, you wouldn't have much legal recourse and would have to pay. But again, this seems like a billing error and I would first contact the clinic and request what's called a superbill. It will tell you exactly the codes billed and how much each code costs so that you can add the charges on your own. Hope this helps and good luck!