Got an overpayment notice, what now? - any advice?

I received a letter saying I was overpaid about $350 on my claim. 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.

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.