Message left: "Attention. Ignoring this will be an intentional second attempt to avoid initial appearance before a magistrate judge or a grand jury for a federal criminal offense. This is the final attempt to reach you to resolve this issue immediately and to speak to a Federal agent call back number 301-637-8978. I repeat 301-637-8978. Thank you."
Apparently the scammer doesn't know that this is not the way judges or grand juries work in the US!
But I'm afraid most Americans don't know this is bogus, either!