Got an overpayment notice, what now? - 18 weeks in

I received a letter saying I was overpaid about $850 on my claim. It has been a long 18 weeks. The letter mentions an appeal window and a repayment plan. Who should I talk to first?

Keep everything in writing and save the confirmation numbers. It saved me later.

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.