Find "Mobile networks"
Press arrow up to access the main menu.
Press Settings.
Press Wireless & networks.
Press Mobile networks.
Activate or deactivate
Press Data roaming to activate or deactivate data roaming.
When the box next to the menu item is ticked (V), the function is activated.
If you activate data roaming:
Press OK to confirm.
Press OK to confirm.
Exit
Press the Home key to return to standby mode.