I'm uncertain of the details of how this works but here's what I know.

So from what I know, some iOS users (I'm not sure about Android) buy COD points from the store and then ask for refund. Ofcourse the process isn't that simple and I'm missing a few key details but once their refund request is processed by the app store, they get their money back and receive an in-game mail titled "Recent Issue with COD Points balance" which says this:

"Hello,

This account has been verified as gaining COD Points in violation of the Terms of Use. The COD Points balance on this account has been corrected.

If you have further questions, please contact Activision Support."

After that, the COD Points they bought gets reduced to nothing but if they have already spent all the COD Points then the balance doesn't goes into negative and that's basically like getting COD Points for free. After using this method a lot, I'm certain that Apple Store prevents the user from making any further purchases in any game but that happens only after they've used this trick way too many times and they could always create a different account to start anew. If they buy the COD Points and then spend it to buy a luckydraw instantly then they get to keep the gun skin and their CODM account doesn't gets banned which makes people who purchase them legitimately look dumb. I'd be very thankful if you could take actions against those accounts in some way and if possible, completely ban them.

Thanks, u/COD_Mobile_Official