I have recently switched to Coles Mobile on the $20 plan (35 day expiry, 3GB, unlimited national calls) and I noticed at the bottom of the Coles Mobile webpage that 500 bonus flybuys points (worth $2.50) are earned for every Coles Mobile recharge purchased in store. This looks like it even applies to the $10 for 10 days recharge option.
Of course, most savvy Ozbargainers should be using a 5% discount eGift card at Coles, which brings each 35 day recharge down to $16.50 for the $20 option (i.e. deducting $1.00 for the 5% discount and $2.50 for the value of the flybuys points).
Per calendar month, that equates to $14.34 and 2.61GB per month
edit: for the $40 recharge (also 35 day expiry and 10GB), this deal works out to be $30.85 and 8.69GB per month
I think they deduct 500 points from your flybuys to reduce price by $2.50. That’s how I understand it.