Belong Mobile $45 100GB 1-Month Starter Pack $20 + Delivery ($0 with Prime/$59+ Spend) @ Amazon AU

Price matching Coles & Officeworks, if you don’t have OnePass or have discounted Amazon Gift Cards to use.

Use it for 3 months + $7, see here – thanks WatchNerd.
Current promo has double data 200GB

Data rolls over and can be transferred to friends/family.
Use Telstra 5G network.