Pay-as-you-go roaming is nearly certainly the priciest option when you're overseas. Although cheaper than it once was, global roaming is still a costly proposition, particularly if you're travelling for over a week. It's absolutely free to get SMS while roaming. By way of example, Optus' postpaid roaming is a bit less expensive than its prepaid roaming.

Again make sure that your phone is unlocked. If it is locked, it is restricted for use on your home carrier's network and you must use your carrier's international phone rates. You're not buying the phone on cheap SIM plans Australia, you're leasing the gadget. If you've got an unlocked phone and mean to produce calls to Australian numbers, it is reasonable get a prepaid Australian SIM card on arrival rates will be a lot superior than using your U.S. network.