This is a Fraud. I called the number. I don't owe anything to IRS. Furthermore, IRS does not call you about outstanding taxes, they communicate through US Mail. Don't fall for it. Call IRS directly if you have questions and report that you received a call with the number so they can be informed as to what's going on.
I've gotten 2 calls yesterday and today. Both from the St.Louis area one number 314-762-6804 and 314-379-0471. The computerized voice left only said that there was a warrant out for me to call them back immediately. This is a scam don't call them back