Got an overpayment notice, what now?

After 14 weeks of benefits I got a notice saying I must repay some of it. This is my first time dealing with any of this. The letter mentions an appeal window and a repayment plan. 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.

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.