Got the same robo call.  Called the number back.  Clearly it's a call center and they refused to give me their name.  So, I said "I'm An IRS Agent" and I need to speak to your supervisor.  They hung up.  I am going to have A LOT of FUN with this phone number.  You can, too.  Just block your number before you call.  Hey, maybe we can collectively get back at these scammers !