I realize collection agencies spend a lot of resources tracking people down to get the money owed, but I am curious as to how they can find a cell phone number.

The reason I ask is because we were getting calls for a woman with the same last name as ours but different first name, once we finally took the call, the guy apologized, next day, he's calling my wife's cell phone asking for the same (different) woman. I have left 2 msg's now to speak with this guy, and now he won't return my calls. I am little bothered that he somehow got my wife's cell phone thinking it was still this other lady.