Same story. This number, and its associated number, 301-882-9975, have been calling me for several weeks, looking for someone I don't know. At first I took them at their word that they were a law firm/collections agency, but as I have a policy of neither answering nor responding to unsolicited calls, I just delete their messages and hope they'll eventually go away. Maybe they are legitimate; but their tactics and evasiveness lead to the suspicion that this is a scam or attempt at identify theft.
Have called me twice this morning and it is only 8:45. As others have said, they are a collection agency that I only managed to talk to once. They are rude, insist that you give them personal information so they can "make sure you're not the person they are looking for". When I told them there was no way I was giving them any information the guy got very aggitated and finally hung up.