Report the calls to the real IRS here:

IRS:   http://www.irs.gov/

http://www.irs.gov/uac/Report-Phishing
[email protected]
http://www.treasury.gov/tigta/

http://www.irs.gov/uac/Tax-Scams-Consumer-Alerts
http://800notes.com/forum/ta-8c2f64bf2b91fa5/irs-warns-of-telephone-scam

•If you owe federal taxes, or think you might owe taxes, hang up and call the IRS at 800-829-1040. IRS workers can help you with your payment questions.
•If you don’t owe taxes, call and report the incident to the Treasury Inspector General for Tax Administration at 800-366-4484.
•You can also file a complaint with the Federal Trade Commission at FTC.gov. Add "IRS Telephone Scam" to the comments in your complaint.