Told I owe money back on my benefits - any advice?

I received a letter saying I was overpaid about $850 on my claim. I cannot afford to repay it all at once. Who should I talk to first?

Thanks for writing this out. I went through something close to it 3 months ago, and it got easier once I kept a simple log of every call and form.

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.