The Broadband number is still manned, though you may have a bit of a wait.
Oh, and posts buried two spoilers deep are only read by the truly thorough 😛
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.