I am unsure of what to do here..

We've had a customer purchase an item FBA and an item FBM, both of which the customer claimed were defective then returned junk parts in the boxes. FBA granted the refund right away and shipped us back his return, but it was just junk, then he did the same thing to us, but we received the package back and could verify the contents ourselves. So I reached out and let the customer know he needed to return the actual product for a refund, to which we got no reply, so I cancelled the return on the note that the product was not actually returned.

He then was able to file a claim with Amazon, they immediately refunded him the amount and we got penalized in our account health ratings for it and even with appealing, our info about being scammed was flatly rejected and we were forced to take a second hit from this customer.

How do I report this customer so he can no longer do this to businesses? How do I file a claim to Amazon about all the scams we get? Who do I talk to about seller support in these situations? Why is there no system set up to stop this fraud?! Customers are NOT always right and as a small business why is Amazon allowing us to be taken advantage of so easily with no proof we EVER produce meaning anything or doing anything to change outcomes?! Signatures, pictures, returned garbage, proof of it all doesn't matter it seems...

Should I literally just stop using Amazon since they don't seem to care about us anyway? Really sad I can't use a world wide sales tool because we keep being frauded by customers with no support from Amazon. As a small business, losing THOUSANDS of dollars since starting with Amazon is just bad business choices at this point, more hurt than good.

What do I do?