Samsung Galaxy Z Flip
Selecting network
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.
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press Connections.
Press Mobile networks.
Press Network operators.
Press Select manually and your phone will search for networks.
Press the required network.
Press Select automatically.
Press the Home key to return to the home screen.