Told I owe money back on my benefits

I received a letter saying I was overpaid about $150 on my claim. I have read a lot of threads here and could not find my exact situation. I did not notice any errors at the time. Who should I talk to first?

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.

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