Overpayment letter from the unemployment office (St. Louis)

After 26 weeks of benefits I got a notice saying I must repay some of it. I am in St. Louis, in case local advice matters. 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.

If you are unsure, free legal aid in your area may help for this kind of notice.