This could happen if you are playing a game on one of the European language servers.
You should be able to change your server back to English and get the correct currency. You may need to clear cache and or cookies in your browser to get away from that little bit of data that thinks you wish to use Euro's.
If that doesn't work, send in a bug report and I will see if there is something the payment department can do to force you to only see your preferred currency.
