There's the fun -- and the challenge -- you don't EVER tell someone who picks up the phone who you are, who you're with, or why you're calling, unless and until they definitively identify themselves as the debtor. FDCPA means you legally can't.
That's why we used Merlin Data. We could identify workplaces, residences, nearby family and associates, just from the info we already had on file: Name, SSN, last known address, last known employer.