Got an overpayment notice, what now?

I received a letter saying I was overpaid about $600 on my claim. I am in Cincinnati, in case local advice matters. I did not notice any errors at the time. Are payment plans possible?

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.