1. Find "Mobile network"
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press Network & Internet.
Press Mobile network.
2. Turn use of SIM on or off
Press the required SIM.
Press the upper indicator to turn use of the SIM on or off.
3. Select default SIM for mobile data
Press Data preferences.
Press the required SIM.
4. Select default SIM for voice calls
Press Calls preference.
Press the required setting.
5. Select default SIM for text messaging
Press SMS preference.
Press the required SIM.
6. Return to the home screen
Slide your finger upwards starting from the bottom of the screen to return to the home screen.