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I've never had to deal with them personally, but they do appear to be a legit agency.
There are some options you have in order to ensure it's a legit debt and not because your identity has been compromised. You can request they verify the debt(s) to you in writing. They'll have to tell you exactly what the debt is, when it was due, and, most importantly, if they have a debt collection license in the state you reside.
Once you receive all of that information, it's important to check if the statue of limitations on the debt has expired. If it has then you are not legally required to repay the debt even if it isn't fraudulent.
If it is in fact your debt and the statue of limitations hasn't expired then you are legally required to pay the debt. From what I understand, these companies will often work with individuals to set up payment plans and/or reduce the amount owed for people who are unable to pay all their owed debt. That's done on a case-by-case basis though, so you'd need to directly contact the company to see if they would be willing to work with you.