So, I was able to successfully sign up for the Eskimo (Singtel) free offer. While researching it, I also ran into a referral code for an additional 500 MB that someone posted on www.ozbargain.com.au (but it turned out every account can generate this code - so if you have a family have the first person use a code from someone else, then the rest of the family can use your code). The important things to differentiate is that there is the 1 GB Gift Code which they e-mailed me and the fixed 500 MB referral offer code. There are different boxes in the App to put them.

Thanks paperwastage !