The IRS will contact you by telephone but only if you're expecting a call from them.
If you're delinquent on the IRS taxes or have paid the wrong amount then the IRS will send a certified letter to your address where you have to sign for the letter.
The IRS will never call you first and demand a payment or face jail time as that is the Fake IRS scammers doing that.
If you get a call from someone claiming to be the IRS you should immediately hang up and never send money to the Fake IRS through gift cards or any other means.
The Real IRS doesn't accept gift cards or other vouchers for payment.
The real IRS number you can call is 1-800-829-1040