Hi and welcome to the forum,
The easiest way to cancel your NOW TV service is by using a Windows or Mac computer (not a mobile device), here's what you need to do...
When you are logged onto this forum using the same NOW TV account as your NOW TV playback device(s): -
You should see something like this: -
Welcome to the forum.
its part of the terms of the service that you have a payment card on file for your account to be active. Instead make sure you cancel your pass now by going to your My Account > My Passes page http://account.nowtv.com/passes and clicking the Cancel option next to your movies pass, then follow all the steps. Once cancelled you will still be able to carry on watching your pass until the 2 months is up but it won't renew after that.
As an extra precaution you can enable the payment PIN on your account to prevent anyone in the household accidentally purchasing anything