Sony Xperia 10 VI
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 Network and Internet.
Press SIMs.
Press the name of the SIM.
Press the indicator next to "Automatically select network" to turn off the function and wait while your phone searches for networks.
Press the required network.
Press the indicator next to "Automatically select network" to turn on the function.
Press the Home key to return to the home screen.