Looks like this deal has been extended.
When using the Coles Express ATM (this can be in the form of a balance check or a withdrawal, I believe), there will be an option to select a discount voucher for use. Select the 15% off prepaid recharge voucher and this will print. Use the voucher at the counter to receive the discount.
If you have an ING direct card, withdraw at least $200 using the ATM so you don't incur an ATM fee and then pay for the recharge using Paywave/Paypass (if the total comes to <$100, or you could pay in $99.99 installments if they allow you to) for an additional 5% off the discounted price.
For Coles Express ATM locations, see here.
oh, shouldnt have bought so many b4 :(