iOS is the operating system software installed on your iPhone. To find out which version you have: Tap Settings, Tap General, Tap About, and view the version number.
If you want to avoid using data when you're abroad, you need to turn off data roaming on your mobile phone. Once done, you can only make voice calls, send SMS and use applications that don't require an internet connection.
Tap Settings.
Tap Cellular.
Tap the indicator next to "Data Roaming" to turn the function on or off.
