Kogan have a 30 day deal for the long weekend that is medium plan (4 GB per month) for $15.00 for 30 days. Vouchers must be activated by 7/3/24. Not sure if when you activate a voucher it automatically adds more time to an existing plan.

Have bought a couple of these to keep me going until they hopefully offer a discounted yearly plan, as my yearly plan runs out end of February 2024. 

Hope this may be of use to someone.