Sounds like you have a Proper Case here
The usual reason for this is that you have a second account, for which you are being charged.
Contact NowTV via Live Chat and explain, and they will be able to see if this is the case, and hopefully sort this out for you.
Get in Touch (all the options, and the best place to start):-
On a screen with big buttons all around, you may find the link you need is under a tiny green arrow, so be vigilant.
Live Chat and Send Us a Message:-
On Live Chat, when you can get onto it, keep your answers short, sweet and prompt, or it will time out on you.
If the person you are talking to doesn’t seem able to understand your issue, ask to be escalated to the next level of help.
You can do this for yourself :-
Go to My Account/Passes & vouchers, find the package you have, click or tap ‘Cancel Pass’, and proceed through the four steps there until you have successfully Cancelled.