Please do report your callers to the FTC, FBI and your state's Attorney General.  More info on this sort of scam here:

http://800notes.com/forum/ta-86217073a9c8dad/ ... 077595690349410
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http://www.consumer.ftc.gov/articles/0258-fake-debt-collectors
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http://www.deadiversion.usdoj.gov/pubs/pressreleases/extortion_scam.htm
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Also read up on the laws and your rights:

http://800notes.com/arts/Jb8EW-eDhQA/harassin ... ou-need-to-know
http://www.ftc.gov/os/statutes/fdcpajump.shtm
http://www.consumerfinance.gov/askcfpb/search ...
http://www.consumer.ftc.gov/articles/pdf-0096-fair-credit-reporting-act.pdf
http://www.consumer.ftc.gov/articles/0149-debt-collection
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Follow the steps in what you need to know. A legitimate debt collector agency should not have a problem with giving you a real business name and address you can google and verify via google street view, BBB etc.
For extortion Scam Operations, file reports with the FBI, your state attorney general and Department Of Justice,FTC & FCC..

http://www.nw3c.org/
http://www.ic3.gov/default.aspx
http://www.fbi.gov/
https://www.ftccomplaintassistant.gov/#&panel1-1
https://esupport.fcc.gov/ccmsforms/form1088.action
http://www.consumerfinance.gov/complaint/

And folks should consider looking at maybe getting call blocking device or phone..
http://www.amazon.com/s/ref=nb_sb_noss?url=se ... s=call+blockers