Overpayment letter from the unemployment office - what worked for you?

After 9 weeks of benefits I got a notice saying I must repay some of it. Any experience at all would help. I did not notice any errors at the time. 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.