Thanks @bhs1928 for your insight! All extremely helpful.
I met my deductible. My portion of the final bill SHOULD be $0. Often, what is billed by the MD’s office does not match what has been negotiated with Medicare (or other Insurance companies). I don’t know definitively without an EOB.
But, for this particular visit, Medicare would have paid their part and my Supplemental insurance should have covered the rest. It never got sent from Medicare to my Supplemental though, because MBD closed the claim without responding to Medicare’s request for corrected information.
I’m actually starting to wonder if all this is just multiple mistakes made along the way, or if truly it should go to the “balance billing / fraudulent billing” hopper.