Before you travel put any other SIM that's not from your regular mobile network into your phone and turn it on. If your phone shows a network name it is unlocked, if it says something like "SOS calls only", "Invalid SIM", "Network locked" or "SIM locked" then your phone is locked into your home network.

Occasionally we have customers who have been told by their carrier that their phone is unlocked, whereas the phone was either not unlocked or the unlocking process was not completed successfully. The best way to check that your phone has been unlocked is to pop in a SIM from a different network (for instance an Optus SIM in a Telstra phone) and see whether you get a signal and make and receive a telephone call.