OPPO A78 5G
It's not possible to make voice calls
Solution 3 of 11: Barring of outgoing calls is turned on
You can block certain types of calls such as incoming calls when you're abroad.
Press the call icon.
Press the menu icon.
Press Settings.
Press Calling accounts.
Press Operator-related settings.
Press Call barring.
Press the required barring type.
Key in your barring password.
Press the Home key to return to the home screen.