When you insert two SIMs into your phone, you can make calls and send and receive messages from both SIMs. You can also select a default SIM for mobile data usage.
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press SIM card manager.
Press the indicator next to the required SIM.
Press OK to turn use of the SIM on or off.
Press the required setting.
Press the required SIM.
Press Mobile data.
Press the Home key to return to the home screen.