Are you NA or EU?

EU appears to have some whitelisting service for credit cards (try live chat support to ask about it?), it is not available to NA but appears to be the solution for them.

For me on my NA account I've dealt with these errors for over a month and a half now, finally fixed it last night:
http://forum.square-enix.com/ffxiv/t...=1#post2573919

Try following the steps in my post and give it a shot if you're NA. Good luck.

I completely agree their system is flawed and bugged but there's nothing we can do about it.

Also live chat support >>>>>>>>> email support.

SE email support is atrocious, contradicts themselves regularly and withholds information randomly I strongly suggest phone or live chat support when possible.
If something is wrong with your card then they can look into the specific errors which you can contact your bank with.