I have been getting buyer fraud on one of my products, they will open an AZ claim two weeks after the package has been delivered saying they didn't receive the package, but the actual package was delivered and there are photos of the logistics delivery.

When they open a claim, Amazon won't look at my complaint and will just refund the buyer's money, recently I've been getting tons of scammers coming in for this product and I don't know what to do, I've opened cases to get Amazon to refund me the money and no one is taking care of it and it's costing my store a ton of money. What should I do?