We got the same threatening message from "Carol" supposedly from the Department of Legal Affairs with the US Treasury, also at 718-880-4021. Thank you for all these posts - we won't be returning their phone call!
I also recovered a call from +1 (718) 880-4021. A man with an accent called me 7 times in one day. When I finally answered he told me that he was from the US Treasury and that I had a lawsuit against me. I asked why did I have a lawsuit against me and he told me that I needed to call a particular number that he gave me and that they would give me the details. I asked why hadn't I been served and he kept telling me to call the number. I didn't call the number. The next day he called me 3 times and I didn't answer. The same man called me again 2 weeks after the first call. I believe that this is a scam. A lot of things that he said did not make sense.