According the the FTC there is a recent scam where people will pretend to be from the IRS and request that you pay your back taxes using an iTunes gift card. This is a scam. The IRS will not call you and request payment via iTunes.
The IRS actually does not take payments via the phone. You can call the IRS and make payments via a third party payment processor. IRS collections agents don’t process payments.
Sincerely,