According to the woman I got on the phone today (to their credit, they have really short hold times) they rebilled to the proper insurance company on the 19th, but that this rebilling process probably also triggered my being sent this additional bill for reasons known only to their automated system. Joy.
I hope the magic pixies in their billing system and the magic pixes at my insurance company resolve this without any further effort on my part. I know this is a stupid amount of effort to go through to avoid paying a bill for under $200, but I have another bill with them for over $200, and I really don't feel like paying $300-$400 (a month's rent, just for comparison) that should be covered by my goddamn insurance (about $90/month) if they would just bill the right company. I have no idea where they even got the information from my old insurance, it must be in their system from the last time I let medical care take a crack at fixing me in 2002, although I don't particularly remember any bloodwork from back then, just an upper GI and over $500 of uncovered foot-problem-related bills (which did, at least, get me able to walk again, so that was actually better than most of my experiences with medical care).
Also, my stomach hurts (yes, right now), and as I believe I have mentioned NONE OF THESE GODDAMN TESTS HAVE GIVEN ME ANY REASON WHY.