@Hazeyeyes
If the phone part of the broadband works, they can ring 150 from a phone on the landline. That will tell Now that there is a legitimate user on the other end.
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.
