Told I owe money back on my benefits - any advice?

After 24 weeks of benefits I got a notice saying I must repay some of it. 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?

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.