Got an overpayment notice, what now?, dental hygienist here

After 16 weeks of benefits I got a notice saying I must repay some of it. I do not usually post, so bear with me. I did not notice any errors at the time. Who should I talk to first?

Read the letter for the appeal deadline and act on it, even if you think you will end up repaying. Then ask about a payment plan.

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.