80GB is a lot of data and some people might be content with a bank of 40GB (+1GB per month) and having a longer "payment-free" period.
Is there now an "Option 3" to activate on the 40GB plan, but BEFORE the first billing date to switch to the $10/month plan? Combined with a $20 referral credit that should give six months of usage without charge?
Don't forget to use the Ozbargain referral for $20 referral credit when activating SIM
https://www.ozbargain.com.au/api/referral/35