I just found this transcript:

" A final notice from the I.R.S. This message is to inform you that I.R.S. is filing a legal warrant under your name and your tax id for the tax fraud and the investigating team of our department is investigating you and your family we have tried to notify you regarding these issue in previous 6 months but we have never got a response from you so it is being considered as an intentional fraud and lawsuit has been filed under your name by the United States government you may call our department number 320-337-8499 I repeat 320-337-8499 call for more information before we download your case into the courthouse thank you."

Source: http://www.nomorobo.com/lookup/320-337-8499

I think they may just be offline or the number might have been shutdown already.