Overpayment letter from the unemployment office after 3 years as a retail manager

I received a letter saying I was overpaid about $350 on my claim. I did not notice any errors at the time. Who should I talk to first?

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

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.