You should see a list of any active passes you have on your account, with a cancel button next to them. Just click cancel and follow the steps all the way to the end.
You'll still be able to watch your pass after you've cancelled until the expiry date.
If you have more than one type of pass you need to cancel each separately.
If you still have trouble cancelling, pop onto live chat and they can help. To get there go to the following help page and click the Start Live Chat button.
