Overpayment letter from the unemployment office - any advice?

After 16 weeks of benefits I got a notice saying I must repay some of it. I cannot afford to repay it all at once. Who should I talk to first?

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 3 months ago, and it got easier once I kept a simple log of every call and form.