Amaysim UNLIMITED 5GB Free for first 30 days (save $44.90).
You need to enter CC details, but then you can remove them afterwards (select BPAY/VOUCHER as payment method and click SAVE).
Will not work with existing SIM cards, please order a new one.
This offer is limited to the first 1000.
They don't 'have a network'
They use Optus 3G4G