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 !
Got the same voicemail. I never answer calls from numbers I do not know. I have blocked every caller that leaves these threatening messages. I look up all numbers to try a get identification, but no such luck. I guess we all will have more of the same until something is done to stop these bogus calls.