How long ago did you sign up? Double data doesn't usually kick in until your second bill at Optus (something I think is illegal but that is how they do it)
Are you getting 50% warnings at 12.5gb? If not you may already have the data but it not just show. You should be able to contact live chat any time to confirm the data has been applied.
With the Netflix, like the op, it's unclear what you mean by 'charged'. What screen lead you to Bruce this? Also as a check ensure you have activated free streaming. You can do so in MYACCOUNT or via the Optus app.