@Anonymous User
At a guess, what you set your password to isn’t what you thought you set it to.
Use the ‘forgotten password’ procedure to set it again:-
https://help.nowtv.com/article/forgotten-password
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.