Overpayment letter from the unemployment office, line cook here

The agency says I reported earnings incorrectly, but I think I followed the instructions. I am in Austin, in case local advice matters. The letter mentions an appeal window and a repayment plan. Who should I talk to first?

Collect your pay stubs and certification records for the weeks they name. Mine showed the error was a date mix-up.

Keep everything in writing and save the confirmation numbers. It saved me later.