Thank you for posting. I just got the same call and rejected it letting it go to voicemail. I will now add this number to my blocked numbers. If the IRS is going to sue me then they can send me something in the mail.
I've received two calls from these idiots thus far and just sent them a text (which, by the way, proves the calls are made from a cell phone) to let them know I've given their number to the REAL Internal Revenue Service to apprise them of their scam and basically, told them to pound sand.