I've actually had good dealings with OTR, specifically on an unincorporated franchise tax issue. It was during COVID so it had to be by phone. It required several calls, during one of which the agent promised to call me back (thought bubble: yeah right). Amazingly two hours later he did.

That said, I think in person is the way to go, and bring TONS of patience and good vibes. And check out the advocate, it has worked for people I know. Good luck!