Full credit to WanderingEgg.
You do get a bonus $500 gift card rather than a $400 gift card, however it is today only (22/10) and ends tomorrow. Available at all stores nationwide.
*Available for New Telstra & Port-in Customers only. Excludes Telstra Pre-Paid, Boost and Belong customers. Offer not in conjunction with any other offer.
Can't port over if your name has been on a sim through the telstra/boost network within the last 30 days (Even with a new sim through optus).