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You can set your phone to select a network automatically or you can select a network manually. If you select a network manually, your phone will lose network connection when the selected network is out of reach.
1. Find "Carrier"
Press Mobile network.
2. Select network
If you want to select a network automatically, press Choose automatically to turn on the function.
If you want to select a network manually, press Choose automatically to turn off the function.
Press OK and your phone will search for networks.
Press the required network.
3. Return to the home screen
Press the Home key to return to the home screen.