I received the same message,  He is IRS officer,giving a phone number, let me call .

There is a fairly common IRS or "tax scam" being practiced by scammers in both Canada and the USA.
USA tax payers should read this:
http://www.irs.gov/uac/Tax-Scams-Consumer-Alerts
Note particularly the links at that site, warning of the scam!

Call received 10/06. Final notice from Internal Revenue Service. Recognized scam and hung up on her.

IRS Scam....Report it: https://www.treasury.gov/tigta/contact_report_scam.shtml