So yo fire up your laptop, open a browser, access the NowTV site OK, but it won’t accept your login details?
What happens? Do you get an error message, and if so what does it say, or does it just hang?
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.