Think about what we might need to know to help you.
Make and model of TV would be a start; if this is a pre-2015 LG TV with the WebCast OS, for instance, that was sunsetted a while back.
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.