Vaya is offering $3 off your first three months for any plan from their "power plans" range or "unlimited plans" (unlimited linked in the deal). All unlimited plans are unlimited talk and SMS, with the sole variable being the included data.
Plans are month to month, not a long-term contract. Vaya uses the Optus network. I'm with them and in Canberra I can get 14/3.5 Mbps.
NB - looking at previous bargains, it looks like a lot of others are unhappy with Vaya's customer service. This may end up not being a great deal for you if you are concerned about that. They have been working fine for me.
Vaya Referral Wiki
$25 credit for the referrer.
Wouldn't even consider Vaya a provider unless you want to be stuck in a nightmare (yes even if you cancel they still charge you). Definitely wouldn't sign up for Vaya for a whopping $9 discount over 3 months.