@Anonymous User
Welcome to the forum.
Usually this is because the pass is on a different account that the user forgot about (maybe an old account you or someone else in the household has).
It's worth logging in with any other usernames and passwords you might have and when you find the right one you can cancel your pass by going to the My Account > My Passes page.
Have a look at the following help page for more info
http://help.nowtv.com/article/Cancelled-but-still-being-charged
and if you are still stuck click the green Contact Us button near the bottom left of that help page and then choose the Live Chat option who can help you further.
