Overpayment letter from the unemployment office - 4 months and counting

The agency says I reported earnings incorrectly, but I think I followed the instructions. It has been a long 20 weeks. I did not notice any errors at the time. Who should I talk to first?

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

Collect your pay stubs and certification records for the weeks they name. Mine showed the error was a date mix-up.