These guys are frauds. the BBB has an F rating for them. They are listed on hundreds of websites for illegal harassment and they are breaking the law and violating the FDCPA. Ignore their calls or if you answer, let them know it is being recorded and your State Attorney General will be notified of their illegal activities. Then hire a lawyer and sue them.
I just got a call from this person too. The message didn't even finish. She started "This is Mrs. Daniels and with Federal Processing and I need a return..." and that's where the message stops. I'm going to do more searches to see what I can find.
I've already been scammed once by another group scaring the crap out of me and after looking at other sites, I now know to ignore these things. Just wish I could get them to stop...