You could try an Indoor antenna. Digital TV is 100% if the reception is okish. Just $15 or so. Return it if it doesn't work.
But note that Optus isn't in a position to help with your FTA reception. If you have an internet connection to a Fetch box then their are a number of streamed channels you can access. Including Netflix, Stan and FetchTV packages. Also catchup TV for the FTA TV channels (not live though)