@Anonymous User
You have a device, such as a TV that is signed in to your account that someone else can access - a child or other family member, flatmate, what-have-you - and you haven’t set a Payment PIN. So anyone with access can order anything,
You have sold, given away, or dumped, a NowTV device or a device with NowTV on without wiping your account details, and someone else is now enjoying it on your dime.
There are further scenarios, but these are the usual two possibilities.
Ring any alarm bells?
Set a Payment PIN on your account so that no-one but you can buy memberships on it.
Check your bank accounts monthly for any other unexpected payments to Now.
That way you can at least nip them in the bud, while you and Now figure out whose fault they are.
