Huawei P30
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.
Press Settings.
Press Wireless & networks.
Press Mobile network.
Press Carrier.
If you want to select a network automatically, press the indicator next to "Automatic" to turn on the function.
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.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.