I have the same issue, they won't accept your credit card. I have to pay via paypal buying crysta.

They may in-fact actually ban your account since you're playing it illegally from the wrong region, yes they really are that anal about it. Lately they are now actively blocking sales of expansions to incorrect regions etc, you would think that they wouldn't do these things since they would lose money from a long-term regular customer right? wrong. Square are very much that idiotic in all things related to money or customer interaction.

Try talking to customer service if you need some comic relief, they are among the worst in the industry. In almost every mmo CS team I've dealt with they will try really hard to fix whatever issue you have, Square Enix CS? You are lucky they will even talk to you for more than 2 mins without cutting you off with a copy and pasted useless answer.