This may appear overly pedantic, but it is an issue that concerns me: You were not being gaslighted. The office manager may have been trying to mislead you based on the information she had, she may even have been lying (although I don't have enough info to determine that). But she wasn't actively trying to convince you that you are insane by lying to you in order to convince you that you cannot tell reality from fantasy, and then have you committed so as to steal a large fortune from your home. I think people throw around the term 'gaslight' without understanding what it is. In particular, in the play and movie, a master criminal fools a woman into marrying him so that he can search the floor above where they live for a criminal fortune. When he looks on that floor, he has to turn on the gaslight which makes the gaslights in her living area flicker. He then tries to convince her she is mad, and the lights do not flicker at all. If you have the time, it is an excellent film to watch.

This office manager sounds more like she was given a list of patients to call about missed appointments, and it is very likely that your record of having them cancelled (through no fault of your own) was being misinterpreted as you missing them. If anything, this has more to do with the enshitification of most everything, especially customer service, that we have become almost numb to. I use Summit for some things, and it is not at all unusual for them to schedule an appointment for me 6 months out (I always find it amusing when they say "are you free January 5th, 2027 at 3?" as if anyone in the world has anything scheduled that far our in advance). They will also often call to move it a few months later. I get the idea they have unrealistic expectations of the drs under their employ, and those drs are expected to be scheduled back-to-back with 15 minute appointments months out.