Told I owe money back on my benefits after 4 years as a bank teller

After 15 weeks of benefits I got a notice saying I must repay some of it. I would rather hear the honest version than the polite one. The letter mentions an appeal window and a repayment plan. 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.