I received the same call too. Here is transcribed text.
"Hello this call is from IRS. That's Internal Revenue Service. The very second you receive this message. I need you or your retained(?) attorney off record to return the call. Base you-at-pam-it's(?) extremely time sensitive. This is Officer Adams cost(?) and my number is 2064515421. Again it's 2064515421(?) seven five to this got this message and do return the call. If you don't return the call or if I don't see her from your attorney either the only thing I can do is wish you good-back(?) as the situation unfolds on you. Thank you and goodbye.