Overpayment letter from the unemployment office - 6 months and counting

I received a letter saying I was overpaid about $1000 on my claim. I am in Oklahoma City, in case local advice matters. I did not notice any errors at the time. Has anyone disputed one of these?

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.

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