Comment by sersi

Sidenote, I remember some people here wondering why websites don't explain why a transaction failed (wrong CVV, wrong AVS or Do not honor, etc...). This is what happens if you do give this kind of error through, don't put some form of rate limiting, etc.. It becomes a convenient site for scammers to test stolen credit cards and you end up being flagged by your payment provider.

Also, it's worth having a relationship with a smaller payment gateway, merchant account provider. It insulates you somewhat.