On the subject of travel, if you don't NEED to use your iPhone overseas, leave it at home or turn it off. Okay, so if you really want to take it and if there's any chance you may need to turn it on, then turn OFF the following first; Cellular Data, Data Roaming. You could also remove the SIM card from your phone so that there's no way it can connect overseas. Then you can join an available wi-fi network e.g. at hotels, airports, cafés OR you could turn Airplane Mode ON and this will not allow your phone to connect via your SIM card. You can still turn wi-fi on and connect this way to the internet. Confusing right? Then there are options like travelsim which offer a new SIM card for use overseas at reduced rates, but still costly overall.