Seems to be a few people with the same problem. Gzero is right, you need to contact EA direct through their online support:
http://support.ea.com/
Support Links/Contact Us:
Once you've logged in with the appropriate email address etc, this will open up a form where you need to type in the game: Battlefield 3, then select billing/purchasing after selecting PC as your game platform. Then email the blighters and tell them you'd like to cancel.
If you do get any trouble with them, you could always contact your bank. Have the payment details ready (you would likely have had an email with them), basically the date and time you made the purchase. As it's not been charged yet you'll need to explain that to the bank.
It's bad EA don't give you a simple cancel button. Shame on them for making it so difficult to manage your purchases.
Edited by deleted (Thu 06-Oct-11 21:50:08)