I tend to agree with @redchiz1 that you probably can’t, but your request is rather ambiguous, and I can’t even tell if you are after broadband or streaming, and how you might be hoping to use it.
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. This week, I are genrally been watching epsidoes on my Sasmung TV