I got a call from this number saying that either my attorney or I should call them back or else I would be sorry. The accent was not US based.

Got the same call as to Bob NN.  said his name was Officer Adam Scott.  He added that if I did not respond right away they would break my door down and lock and bolt it so I couldn't get back in.
Westchester County, NY    The foreign accent sounded like a French accent.

He left message on my machine stating IRS Internal revenue service Officer (I can't figure out name)  calling for a time sensitive matter. Advised  to return call immediately. Otherwise ......His a US based. His accent sounded like he was not raised here.

IRS: http://www.irs.gov/uac/Tax-Scams-Consumer-Alerts
       http://www.irs.gov/

Please do file reports with the FBI, your state attorney general and Department Of Justice,FTC & FCC..

http://www.ic3.gov/default.aspx
http://www.fbi.gov/
https://www.ftccomplaintassistant.gov/
https://esupport.fcc.gov/ccmsforms/form1088.action

Also read up on the laws and your rights:

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

And see:

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

Thank you for useful links. I will follow your advise.