iiNet has released a new range of SIM only no-contract mobile phone plans. The $19.99 2GB SIM Plan is a good plan with 2GB for under $20. You will need to decide whether you need more than $400 call and message credit each month (it works out to be about 180 standard 2-minute calls). Otherwise you can add unlimited calls and SMS for an extra $10.
The cheapest $19.95 plan competes well with the super-popular Vaya $18 Power Plan, with slightly more data for a couple of dollars more. You do get less call credit and it will be up to the individual whether the trade off of calls for data is a valuable one.
Another good plan is 9GB SIM Only Plan for $49.99. This plan include more data than others at the same price, plus you get 300 minutes of international calls.
The iiNet service still operates on the Optus 4G network.