It may not work for everything, but if it ever comes up again, do try reporting them to your state's department of insurance (or whoever keeps tabs on them). I kid you not, I got a call at 9am on a Sat not from my insurance co, not from the co that owns them, but from the co that owns them. "heeeey, bestie, why did you report us to the state board of insurance? bestie, it was just a misunderstanding, of course we're going to honor that approval! idk even know how the wires got crossed!"
I told them I wanted it in writing both to me and to the state. I then spoke to the case worker w/the state and he said, "oh for sure they'll follow through, we take this very seriously. and if they don't you just call me back, here's my direct line." I didn't not expect that kind of service from a governmental agency.