Just ported over to these guys. Great deals. They use the Optus network. Discount in price/extra data is only for first 12 months, so perhaps set a reminder if you want to shop around in a years time. No contract period either.
The 100GB plan is just a 12 month price cut, where as the 50GB is a price cut of their 20GB plan + additional 30GB per month. So keep in mind that after a year, the 50GB will drop down to 20GB. The 100GB should stay at 100GB, however the price will go up. There is also 8GB for $14 a month. Good for your parents who probably never use their data.
Mod: Referral link removed
Shouldn't this company be banned from here? Wait for all the negative responses.