Please send us your suggestions for Australia and help others to get a reasonable SIM-card for their next trip!
There are 3 network operators: Telstra, Opts and Vodafone who all offer could coverage in urban areas. In rural areas you always have to expect problems.
To buy a prepaid SIM card you have to register with a passport.
LTE frequency-bands can differ from international standards!
International offers and reseller with international shipping: