Overpayment letter from the unemployment office - first time posting

The agency says I reported earnings incorrectly, but I think I followed the instructions. I worked as an HR coordinator before this. The letter mentions an appeal window and a repayment plan. 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.