You can hope that the cancellation button works properly (which it appears not to) & you get some luck - I've cancelled 3 times so far & still get billed, you do get a refund after a painful online chat with customer services though, they do dispute that you've ever cancelled but must know that you really have because they don't quibble on the refund.
Go to My Account, Select Passes & vouchers & the cancel button is in there (for all the good it does)
