The IRS will not call you. They send letters via US Mail. The IRS won't ask you to pay in i-Tunes cards. The IRS will not wish you "good luck as the situation unfolds". Trust yourself and your instincts - do not let a bully intimidate you by threats that are nothing but hot air (and bad breath). This is a SCAM.
Do not answer calls you don't know and never call them back.
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Here's a link to the IRS website: Phone Scams Continue to be a Serious Threat, Remain on IRS “Dirty Dozen” List of Tax Scams for the 2016 Filing Season