Can the phone automatically switch to the mobile network when Wi‍-Fi is absent or weak?

Yes. You can set the phone to automatically switch to a mobile network when there's no available Wi‍-Fi network or the signal is weak.

1. Open the Quick Settings, and then tap the Wi-Fi icon to turn it on.
2. Press and hold the Wi-Fi icon to go directly to the Wi‍-Fi settings.
3. Do one of the following, depending on your phone's Android version:
   • Android 8: Scroll down the list of available Wi‍-Fi networks and tap Wi-Fi preferences > Advanced.
   • Android 7 or earlier: Tap > Advanced.
4. Turn on the Auto-switch to mobile network option.

Note: This feature may not be available in some phones.