Got an overpayment notice, what now?, retail manager here

After 20 weeks of benefits I got a notice saying I must repay some of it. There are 13 people counting on me, so I am trying to be careful. The letter mentions an appeal window and a repayment plan. Who should I talk to first?

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.