Clover, am sure you do have 3 days to pay. Think you can either go online or call a 1300 number and pay over the phone with a card.
Honestly, it's such a straightforward drive up the M1, over the Gateway and towards the sunshine coast it far outweighs the inconvenience of calling up to pay the toll. Going anywhere near the CBD is icky and way more time consuming. You'd probably save 20-30 mins to go over the gateway.
Safe driving.