Optus currently has the 186 Day 130GB Pre-Paid Sim on special for $120 (Was $160) and Cashrewards has $53 cashback so using math it's $67 after cashback which equates to $11.16 (21GB) per month.
Special terms
- Cashback is issued by Cashrewards, not Optus.
- Cashback is eligible on new sign ups only.
- Cashback is paid once per order/transaction, regardless of the number of plans purchased on that order.
And before all the questions start - there's no mention of needing to activate in the special terms.
If you're worried about it take a screenshot.