Told I owe money back on my benefits after 16 years as a recruiter

After 6 weeks of benefits I got a notice saying I must repay some of it. This is my first time dealing with any of this. I cannot afford to repay it all at once. Has anyone disputed one of these?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.