Wouldn’t be better if there was a way to add passes or view your account through Mobile App on iOS/Android so could update cards details, but please don’t say can’t be done because in App for Netflix has section to take you to your account.
@Anonymous User in the meantime using the webpage on your mobile allows you to add passes, update your card when necessary and generally manage your account.
It would be better though if was added to app to save time because I do check my account through Netflix app all time and saves time opening browser to sign in.