OPPO A57s
Android 12.0
1 Find "Call forwarding"
Press the phone icon.
Press the menu icon.
Press Settings.
Press Calling accounts.
Press Advanced settings.
Press Call forwarding.
2 Divert calls to voicemail
Press the required SIM.
Press the indicator next to the required divert type.
Key in 707 and press the confirm icon.
707
3 Return to the home screen
Press the Home key to return to the home screen.