I only have the ps2 version. But it should be the same way with the PC version.
First goto:
http://www.ffxionline.com/modules.ph...showpage&pid=9
and on the 3rd step goto :
"Pay Content ID"
then you'll end up here:
http://www.ffxionline.com/modules.ph...howpage&pid=15
Then the middle option is to cancel the contract. Sorry, but I never tried that option. You'll mostlikly have to type in your user name and password to log-in and from there there might be 2 button for yes or no. Again, i have not used that option before. But i hope it helps.