Surprise PCP Balance Due

I’ve been seeing the same PCP for at least the 2+ years. Every time I finish an office visit I ask the office staff how much is due. I would always pay on site for what they said was due which was about $44. Today was a different experience. Today they said the total for the visit was considerably higher than all my prior visits at $148(my insurance hasn’t changed in 2 years). I asked them to confirm and they said it was correct after checking with the office manager. I asked some more questions which led to the office staff involving the office manager who then told me my balance was actually greater by $80 than what they had just told me seconds ago and was actually $219. I asked why that was the case and she said it was because the visit was actually a “class 4” visit (99214) instead of a “class 3” (99213) visit which is where the different number came from. I asked what the difference in classification was and she said it was up to the doctors description. That didn’t feel like a very legitimate answer so I pushed a bit more and asked if it was just an arbitrary decision made by the doctor or if there are descriptions that that differentiate these level of visits. I cut to the chase and asked for those descriptions in writing to which she Googled the difference between the class 3 and class 4 visits. Of course my visit clearly fit into class 3 but when I asked her to ask the doctor to reconsider his classification based on the written descriptions from google the office manager provided, they refused because the doctors said if they did it for me they would have to do it for everyone. Around this time, the office manager told me that not only did I owe the $219 for todays visit, that the office and billing company had failed to do their jobs correctly and I actually had a several year balance of well over $800. I was shocked by this and explained I had received zero notice of this balance. The office manager even admit that it was their fault.

I share this story because I want to know what options I have. Logic would tell me that if they made the billing mistake that at this point the “bad business” would have already been written off. Even if that isn’t the case, I have received zero notices of this balance and it hasn’t effected my credit at this point which means they haven’t been looking for the money either. Do they have a right, all these years later, to expect me to pay this balance even though they admit it was their fault to begin with? If so, are there any options I have? I wonder if I can issue a complaint to the medical board or some other entity?

I also have a voice recording of the office manager admitting fault

Please help