I called back. The person gave me a name and badge number. He told me they mailed out a letter in August and November and that they would not mail anything more. And I looked up the phone number while I was talking and advised him that is coming up as a scam and he disconnected.
Message received on 1/14/16 and 2 on 1/15/16 stating it was the IRS and they were filing a lawsuit against me and I was to call them back immediately. Caller ID said it was Washington, DC cell phone.