Huawei P20
It's not possible to use Wi-Fi
Solution 1 of 4: No connection to a Wi-Fi network is established
You can use Wi-Fi as an alternative to the mobile network when establishing an internet connection. This way your phone doesn't use mobile data.
Press Settings.
Press Wireless & networks.
Press Wi-Fi.
Press the indicator next to "Wi-Fi" to turn on the function.
Press the required Wi-Fi network.
Press Password.
Key in the password for the Wi-Fi network and press CONNECT.
Press the Home key to return to the home screen.