Goverment Grant Scam

I just got another one of these phone calls I told the person to stop calling me. He he called me from an unavailable number and told me my number was selected to receive a government grant and he never talked to me before. I told him to stop calling me and hung up on him. I first started getting these phone calls starting in the middle of July. The first time I called the number they gave me to call and the guy told me there would be an activation fee before he said anymore he hung up. When I called the number back it was busy or no one answered. Since than several different people have called from different phone numbers showing up on my phone, then phone numbers showed up showing all 000-000-0000, and now they show up unavailable. Since the first time I have told whoever called to stop calling me and I told them I know it is a scam. Some have had foreign voices and others haven't. Calls have been from both men and women.