Do: Turn Off Data Roaming. Before you get on that plane (or train) to leave the country, turn off both data roaming and cellular data on your phone. This will prevent your device from connecting to towers or networks along your journey, leading to pricey roaming charges from your carrier.
If you're relying on Wi-Fi, it's important that you turn off cellular data on your phone, otherwise you may inadvertently rack up international roaming charges. Skype, Google Hangouts and other apps also let you make free video calls with other users over an internet connection.
Check your Cellular Data options and turn off Data Roaming. In the Settings app, tap Cellular, or Cellular Data, or Mobile Data. Turn on Cellular Data, then tap Cellular Data Options. Turn off Data Roaming.
Airplane Mode turns off your device's ability to connect to cellular networks (meaning it can no longer send or receive calls or texts, or use data). As it is no longer accessing local cellular networks, it will not be charged roaming fees (caused by your device connecting to networks outside its home region).
While it depends on your device, most modern phones allow you to use Wi-Fi even when in airplane mode. When you enable airplane mode, Wi-Fi will shut off, but you can enable it again manually. In some cases, Wi-Fi might not shut off when you turn on airplane mode in the first place.