Overpayment letter from the unemployment office

The agency says I reported earnings incorrectly, but I think I followed the instructions. I worked as a teaching assistant before this. The letter mentions an appeal window and a repayment plan. Are payment plans possible?

If you are unsure, free legal aid in your area may help for this kind of notice.

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.