Debt collection people.

They use a fear-based recording tactic to get you to respond.  Once you respond, they will trace your call or ask for info in attempt to go after you for a dept that is either yours or they have tagged it to you for some reason.
ADVICE - DO NOT CALL BACK!  If you are concerned about a credit issue, get your credit statement.  
A lot of times, whatever debt they are searching for is out of the statue of limitations and has been sold to them.  So, you may have no obligation to pay.  They are basically fishing to find somebody or someone to pay them.  What they claim you may owe them may not even be on your credit history due to statur of limitations etc.
Bottom Line - Don't call back!  Check your credit!  Let them fish elsewhere!

I love the scary recording they use.  It is hilarious.  Also, the line "of course, I need to speak with you."
Yeah, right...  I need to speak with you means we are trying to find you and pin some sort of debt on you and since we have no legitimate way of contacting the debtor we will use this tactic to scare you.

Simply...hilarious.  What a crappy line of work...

Cheers

1 been getting these very scary recording male voice at the beginning on my home fphone, 1 made a mistake and called them back,it belong to a collection agency and they claim about a debt with master card, none of the person living at my home owe anything to master card, and they insist that the call will never stop unless 1 pay 1750 that is owe to them, this look like a scam,ray, the supervisor is even willing to cut the debt in half if 1'm willing to give him my personal informations

someone is calling my home number anytime even on night hours, i think is one of these collection agencies,but don't any debt with anybody