Found at OzBargain
New-to Amazon Prime (including trial) customers will enjoy 3 months (90 day) membership. Existing Amazon Prime (non-trial) customers will receive a AUD15 Amazon gift card directly into your Amazon wallet.
"Offer subject to change. Terms and conditions apply. Offer is available to eligible Mastercard World and World Elite cardholders signing up to Amazon Prime Australia or existing Amazon Prime Australia customers only. The offer is only valid for redemption until 31.10.23. Eligible Customers will receive 3 months (90 day) Amazon Prime membership courtesy of Mastercard when they sign up for a new Amazon Prime account or existing Amazon Prime customers will receive an AU15 amazon.com.au Gift Card. After the 90-day promotional period, you authorise Amazon to charge$6.99 AUD/month for Amazon Prime service. Cancel anytime by visiting ‘Manage Prime Membership’ in ‘Your Account’ on Amazon.com.au and adjust your membership settings."