Hi thee and welcome
China and Australia use different networks. China uses CDMA, Australia uses GSM. The Sim slots are for global usage within China, they are not for use as the primary network, it needs the CDMA network for this, which only exists in China, India and US (Verizon networks)
Australia like the rest of the world only uses the GSM network and this is why it is not working. Its a technical limit which you cannot get around.
You do get Chinese clones that are destined for oversears markets that GSM but these will work when you pur the SIM in, if the SIM is not functioning and you used a few, its this that's the cause sorry.