Got an overpayment notice, what now? - what worked for you?

I received a letter saying I was overpaid about $750 on my claim. I am in Tucson, in case local advice matters. I cannot afford to repay it all at once. Has anyone disputed one of these?

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 made the follow-up calls so much easier.