Told I owe money back on my benefits - what worked for you?

I received a letter saying I was overpaid about $300 on my claim. It has been weighing on me all week. I did not notice any errors at the time. Has anyone disputed one of these?

Collect your pay stubs and certification records for the weeks they name. Mine showed the error was a date mix-up.

Keep everything in writing and save the confirmation numbers. It saved me later.