A small number of providers offer unlimited mobile plans in Australia. Telstra, Optus, Vodafone, Felix Mobile, Belong, and Dodo all have mobile plans that you could call "unlimited", but there are still caveats to be aware of.
While these plans have unlimited data option, the catch is usually speed. After you go through your primary data allowance - the 50GB, for example, your plan comes through - you'll get unlimited data but at a slower speed. Typically 1.5Mbps.
Telstra, Optus, Vodafone, Dodo, and Belong have all moved to this model for even some of their cheapest mobile plans. Vodafone even has endless data available on prepaid.
Felix Mobile is an interesting alternative, where you get truly unlimited data, but you're restricted to speeds of 20Mbps. That's a lot faster than 1.5Mbps, but not quite as fast as a normal plan, where speeds can easily hit 100Mbps.