Hi @RosieMcs
Unfortunately there is no telephone number for TV Membership customers, where live webchat is your best option by clicking on the green chat online button towards the top of this link page below.
https://help.nowtv.com/article/how-to-submit-a-complaint
There will be a real person at the end of the live chat service (don't click on the get help quicker button which is not a person, but an auto chat bot).
If you do contact live chat, there should be a reference number from NOW on your bank statement and if you quote this number it should help NOW live chat find the account in question where you have an active Membership.
Before contacting live chat I would also try the account Finder button on this link page below, just in case you have created more than one account and looking at an account which is dormant with no active Membership to cancel.
I am assuming on your bank statement the payment is made to NOW / Sky and not a third party such has Apple, Amazon etc.
https://help.nowtv.com/article/find-an-account
