I don't understand what your problem is...why don't you just download a NA POL Viewer(free) from Playonline website and use that to update your information? On PC, you were probably trying to use a different region POL. You
cannot update your NA account information from an EU playonline, but like I said before POL viewers are free. EU Playstation won't work as well, since you'd be usng an EU Viewer.
I have the European version of the game, currently living in the US and never had any problem wtih updating the game/billing information.
Also, SE customer service will help you in these kind of situations. Just make sure you have a long distance call card since you have to contact the NA customer service and ask them to update your information for you. I don't recomment this method since long distance calls are costly and downloading PoL Viewer method is free/fast/convenient.
Too long didn't read/understood/whatever version:
FINAL FANTASY XI Official Web Site - download this to update NA accounts.
FINAL FANTASY XI Official Web Site - and this for EU accounts.
Note: If you don't have the Windows Vista Operation System, you can simply torrent the XP versions or borrow a Viewer disc from someone.