Before asking, yes I am on the $100 a month prepaid plan, yes I have a Netflix paid subscription, yes, it has been set an SD(standard definition),(just looked through other complaints and made sure all of this was correct), and yet Netflix is still using my personal data. This isnt okay. When it says "Free mobile TV Streaming", one would usually assume that it's free. Used heaps of data on a service presumed to be a bonus part of my plan, and no I also don't chromecast or stream to other devices, just use my phone.
How do you know its using your data?
If its by looking at the Optus data usage breakdown then all data that passes through your phone is shown there and allocated to an app (e.g. Netflix). However this data isn't counted towards you monthly allowance. You'll note the main Total Data left indicator doesn't decrease if all you're doing is watching SD Netflix.
As peter mentioned above, the Data Breakdown page on the App displays all of your usage including zero-rated services such as Netflix. This means you'll see Netflix listed. There's a message at the bottom of this page that explains this further. If you would like us to take a look into this for you, please send us a private message confirming your phone number, full name and date of birth.