I just got a call from this number today; first time, I think. I really think all these guys, if they are collections sleezoids [I have no debts!], just pass target victim's numbers around some sort of collusive system of credit company goons who buy up debts cheaply and then do whatever it takes to collect them from anyone they can get to pay. They often go after people who have been through a bankruptcy, even many years before, counting on fear and intimidation of the people who have already gone through hell before they had to file. Credit card companies cut deals with these sleezoid companies, some of which are firms of attorneys who use auto dialers and/or hire people who do nothing but make calls...that's one reason you often don't get an answer if you pick up, or you get a hang-up.
I ignore all my land line calls if I don't recognize the number. Soon, I will get rid of my land line and I'll be happy to tell AT&T why.
Any legitimate debt collection agent must send you a letter by USPS with proof of the debt you owe and this must happen within a certain time frame. If you have a debt you are concerned about [again, I don't, and I get these calls anyhow.. guess why... I did a bankruptcy a few years ago], I'd look up the laws relating to collections, or even do a quicky consult with an attorney about that topic, often for free. The information should give your mind some relief of the anxiety and fear that the sleezoid collections companies clearly try to take advantage of.