Comeplete scam. They say they are calling from the IRS and you are going to be arrested. When they call now I have a loud air horn I blow into the phone. Gets some interesting reactions.
Some crap about the US Treasury and ignoring the call would be an "intentional offense" to avoid initial appearance before magistrate judge or a grand jury for a federal criminal offense . It was pretty nonsensical, as if the script was written by a non-English speaking person.