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 Applications.
Tap Settings.
Tap Wireless and network.
Tap Mobile networks.
Tap Data roaming to turn data roaming on or off.
When the box next to the menu item is ticked (V), the function is turned on.
