i got calls from this number as well on the same day as you. they said they were with the IRS and they had some leagal matter that they were asking for money saying i owe money to the IRS and they wouldn't explain why and proceded to yell when i asked for documentation.
I got the same message claiming they were the IRS.
"We have made several attempts to reach you. This call is "OF-FISH-SHI-ALLY" (She was obviously told she needed to practice saying that word) a final notice from Internal Revenue Service. The reason for this call is to inform you that (awkward pause as she tries to read the next line of the "script") the IRS is filing a lawsuit against you- (awkward pause- I assume her grammar isn't good enough to remember the difference between a period and a comma) -an urgent call-back is necessary. 202-536-5775 See you in "Zee Court House." (You know, THE court house. The only one in the entire country. That's where she'll see you.)
Exactly same message on same date - at least she sticking to the script. You would think that if someone was pretending to be from the IRS and sent threatening messages, there would be something you could do... other than make complaints here. At least its hoped that these posts might prevent someone from falling for this crap