these are scammers pretending to be IRS,i already contacted the US treasurary to make them aware of these guys,and i also alled the FBI

They are well aware of the problem, and have been trying to warn people about it for a LONG time!

There is a fairly common IRS or "tax scam" being practiced by scammers on both Canadian and USA residents.
USA tax payers should read this:
http://www.irs.gov/uac/Newsroom/IRS-Reiterate ... -Telephone-Scam

Short answer:
The IRS never initiates a contact via phone.
They always send a snailmail first.