Voice mail that said, call back as soon as possible before we proceed in any legal manner. Both times it was a mid Eastern woman's voice and very robotic.
My wife just received the exact same message. This is a total scam. As CWG40 said, the IRS only contacts you via mail. These people are low life scum bags that scare uninformed people into giving them money. There is a reason these calls are recorded now. DO NOT GIVE THEM ANYTHING. I saw one "IRS collector" accept a Target gift card as a form of payment.