Got an overpayment notice, what now? (update)

I received a letter saying I was overpaid about $850 on my claim. The letter mentions an appeal window and a repayment plan. Are payment plans possible?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.

I asked for a waiver and a plan in the same call, and they gave me both forms. It was less scary than I expected.