When did you buy and how far away are they coming from? What was the last ETA date? I can tell you as a seller, you can't upload a fake Aust Post tracking number. The system won't allow it. I have made errors where one number was wrong and it told me the tracking number was invalid and to try again.

If the ETA has well and truly passed, I mean at least 2 weeks passed, contact the seller. If you get no joy, open a dispute. If the items are coming from China, which I suspect they are (their tracking always comes up as invalid until it's delivered), don't let them talk you into resending the item. Always opt for the refund. If they ask you to wait another week, that's not unreasonable, but after that, refund.