This is the fake government grants people. Calls knowing my first and last name and tells me he is from "government grants with the federal government of the United States." It is super fake sounding though because the government does not give $ to people for being "good citizens." Says you can get a money order or gift cards to several retailers.
I just asked if he could call back at a later time. Sometimes I do this to see if they can be more persistent and then require a written letter or something. Of course at this point I already thought it was totally fake. He replied that this was my last chance to receive payment.
https://www.consumer.ftc.gov/blog/fake-government-grants-real-refunds here is the federal trade commission site detailing this.