Leave it alone and don't return the calls since you're playing into their hands. Ignore the calls entirely if you can along with possibly stopping them from leaving messages. No kind of answer, no chance to threaten you.
They called six times on May second. Three calls with another call WHILE they were calling me the first time. The call waiting call was bumped to voice mail (I know. Confusing) and message was actually left. IRS scam. I call them back on my home phone, fast busy. !!BUT!! When I call back from my cell, it rings twice and then I get a notification pop up on my screen asking me to connect to my Wi-Fi for better calling connectivity. Sounds like they're trying to get WiFi pass codes to get into your computers and such. I wonder where they're really calling from. Indonesia? China? The North Pole? Someday maybe we'll find out.
I received a call this afternoon stating that it's the IRS and I am being sued. Pretty scary. Luckily, I heard about this type of scam. I wonder how many have not?