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

The agency says I reported earnings incorrectly, but I think I followed the instructions. I do not usually post, so bear with me. 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 settled down 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.