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

I received a letter saying I was overpaid about $950 on my claim. I have read a lot of threads here and could not find my exact situation. 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 got easier once I kept a simple log of every call and form.