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

I received a letter saying I was overpaid about $350 on my claim. I would rather hear the honest version than the polite one. I cannot afford to repay it all at once. Has anyone disputed one of these?

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

Keep everything in writing and save the confirmation numbers. It saved me later.