Got an overpayment notice, what now? after 3 years as an operations analyst

The agency says I reported earnings incorrectly, but I think I followed the instructions. I did not notice any errors at the time. Has anyone disputed one of these?

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.

Thanks for writing this out. I went through something close to it 8 months ago, and it got easier once I kept a simple log of every call and form.