looks like most of Australia is useing 900 band some parts have 1800 you don't have 900 the link is a map of where 1800 should work. you also need to call customer service and have international service put on you should leave it on for a month or 2 if you take the discounted plan because international roaming sometimes takes a while to hit the billing system http://www.gsmworld.com/cgi-bin/ni_map.pl?cc= au&net=voif its real important that you have service over there go on ebay and get an unlocked quad band gsm phone