Overpayment letter from the unemployment office

The agency says I reported earnings incorrectly, but I think I followed the instructions. It has been a long 19 weeks. 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.

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.