Welcome to the forum. Sounds like the pass might still be active, try going to your My Account > My Passes page http://account.nowtv.com/passes
and if you see an active pass click cancel and follow the steps all the way to the end until the cancellation is confirmed. you might want to take a screenshot of the cancelled pass as well.
If you've been charged you could try talking to live chat, explaining the situation and seeing if they can do anything for you. To get there go to the following help page
Welcome to the forum.
If you don't see any passes on your My Account > My Passes page then you may be logged into the wrong account and the charges will be coming from a different account.
Might be worth checking you haven't got any other NOW TV accounts, it often happens that people set up more than one account to take advantage of different promotions and explains why they keep getting payments made even when they seem to have cancelled everything. Alternately you might be signed into an old Sky ID you have from having had Sky TV or broadband in the past.
The following help page will explain how to track down other accounts.
If you still can't find where the payments are coming from have a word with Live Chat they can help you track down where the problem is. To get to live chat go here