Go into the website of the company, and see if you can add credit to it from Aust.
This "might" extend the life of the esim.
Then after adding credit, say $10 Aud, buy the data pack from it.
$10 is not too expensive, and you would only loose that.
But who knows, that $10 might extend the life of the esim.
If nothing works, then the other way is just to buy a new esim, with a new number, and start buying/adding credit to the new number, and buying a data and talk pack from the new esim.
Usually, when you buy an esim, the phone number attached to that sim, will show up in sim 1 manage my sim too.
Most companies will send the esim info in an email, and you just need to use the camera on your phone to scan the QR code in the email, and that's it.