Huawei P30
Android 9.0
1 Find "Carrier"
Press Settings.
Press Wireless & networks.
Press Mobile network.
Press Carrier.
2 Select network automatically
If you want to select a network automatically, press the indicator next to "Automatic" to turn on the function.
3 Select network manually
If you want to select a network manually, press the indicator next to "Automatic" to turn off the function.
Press OK and your phone will search for networks.
Press the required network.
4 Return to the home screen
Slide your finger upwards starting from the bottom of the screen to return to the home screen.