Hi Glen,
I'm not an expert here, but just googled Australian consumer law and found these
https://www.consumer.vic.gov.au/prod...ged-in-transit
In Vic it seems pretty clear that they would need to sort it out, and if they can't, you're entitled to a refund
https://www.accc.gov.au/consumers/sa...ducts-services
The federal body seems to have the same sort of take on it. There is a link in this one to the consumer protection agency, and they might be able to help chase things up. My initial thought is that most retailers would be pretty keen to listen to these guys if they come knocking.
As a lot of mates have told me in the past, documenting everything helps, and it sounds like youre doing that
Good luck with it!