Overpayment letter from the unemployment office - any advice?

I received a letter saying I was overpaid about $950 on my claim. 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 10 months ago, and it got easier once I kept a simple log of every call and form.

Read the letter for the appeal deadline and act on it, even if you think you will end up repaying. Then ask about a payment plan.