I'm dealing with a similar thing right now where the "insurance" company says something is covered and they will "adjust" it any day now, while the "provider's" billing agent continues sending us fraudulent bills with fraudulent charges. The services were actually provided in a hospital and the hospital's bill was already paid, making these charges baseless for two separate reasons. It's like if you bought food at a supermarket and then a few months later the cashier themselves sent you a bill for several hundred dollars.
So every few months I call them up, tell them that there are fraudulent charges on their statements, and if they send me a payoff statement or corrected bill I am willing and able to pay it in full. They respond that they cannot do that, but emphasize it's really important for me to pay the other charges by their fabricated "due date". I reiterate that I'm not going to pay part of their bill only to have the matter not resolved when they keep sending me fraudulent statements, and that presenting a correct statement is their responsibility. There are certainly better uses of my time, but at this point this medical shakedown cartel is so out of control it's all of our responsibility to hold the line.