I had the same experience. I reported them to the Federal Trade Commission. You should too...the web site is https://www.ftccomplaintassistant.gov/Information#crnt&panel1-1
They also have a phone number which is quicker.
Very rude people on the phone. Demanding to speak with me and I wouldn't tell them who I was. After i ask him who he was stated from the IRS and said its a yes or no answer are you so and so.
Caller claimed he was a calling from US Grant funding to award me some grant money in the amout of 8000 dollars then gave me this number to call for verification. I called the number then the guy told me to never to call that number again or he would sue me.