Overpayment letter from the unemployment office (update)

I received a letter saying I was overpaid about $750 on my claim. I am in Columbus, 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.

Thanks for writing this out. I went through something close to it last year, and it got easier once I kept a simple log of every call and form.