I took my mobile to Oz last year and the year before,my phone is SIM-lock
free,make sure you have done that too.
The first year I used Vodaphone $25 for a simcard including $25 prepaid
value.it worked fine all over Oz
The second year we used Communic8,by Telstra,simcard and $25 value,but
,Telstra didn't allow us to SMS to the Netherlands,while Vodaphone did,they
don't tell you in advance which countries can and can't be reached,
therefore I recommend Vodaphone,prices are the same and Vodaphone works
worldwide so why take a chance.

enjoy Oz
J.V.