The IRS does not initiate contact via a phone call, they first send postal letters.
The IRS does not threaten arrest.
The IRS does not demand immediate payment over the phone.
The IRS does not ask for Credit card, Debit card, or prepaid money card information, at all.
It is a scam ran by offshore criminals attempting to trick you into sending them money.
Hang up and report the call here:
https://www.treasury.gov/tigta/contact_report_scam.shtml
More info:
https://www.irs.gov/uac/report-phishing
https://www.irs.gov/uac/newsroom/phone-scams- ... 6-filing-season
Do report the calls, the criminals are tracked down and arrested (Thanks for the link Mutton):
http://money.cnn.com/2016/05/25/news/irs-impersonators-scam/