Samsung Galaxy A3 (2016)
Android 5.1.1
1 Find "Voice call"
Press Phone.
Press MORE.
Press Settings.
Press More settings.
Press Call forwarding.
Press Voice call.
2 Divert calls to voicemail
Press the required divert type.
Key in 707 and press ENABLE.
707
3 Return to the home screen
Press the Home key to return to the home screen.