Yes, this is a scam. The Gov does not give out grants over the phone without you having applied for them in the first place. Your caller is a scammer who will want you to send him cash first (Western Union, Green Dot Moneypak, whatever) for shipping, handling, whatever, before he will send you the grant. There is no grant. It's all a big fat lie to trick you into sending cash to the scammer. Don't fall for it.