Amazon support scam - 1(800)978-0556

I got a call from my family letting me know my grandfather was just scammed out of $6,000 from a fake Amazon support number. They sent an email letting him know that an order he never made was being shipped, and had a number to call if he didn’t place the order (1-800-978-0556). He called them, gave them the order number, and they said someone from Delaware had gotten a hold of his credit card number to make the purchase. They let him know the only to remove the charge was to give them the codes for $6,000 worth of Visa (or Amazon?) gift cards, which he went through with and gave them.
I’m pretty new to the tech-scamming game, and don’t really know what to do with this. I’ve called the number a few times just to waste their time (and to vent my anger), but that’s about the extent of my abilities right now. Any help I could get would be greatly appreciated. Thank you