Click Frenzy deal, apparently. Unsure if you can use 5G (anyone?). You might be able to stack with Shopback cashback if you visit the link on desktop and activate using their browser extension.
From their website:
Get it for $8 with 40GB total data for use in Oz on activation, and 40GB total data on your next two eligible $30 Prepaid Plus recharges. Plus activate by 30 June 2022 to receive $15 Bonus My Credit which you can use towards your next recharge.
15GB My Data + 25GB bonus data for next two eligible recharges within 90 days of activation. 28 day expiry. Offer ends 31/05/22. T&C apply.