Samsung Galaxy S9
Android 8.0
Select help topic
1 Find "Voicemail number"
Press Phone.
Press the menu icon.
Press Settings.
Press Voicemail settings.
Press Voicemail number.
2 Save voicemail number
Key in +447836121121 and press OK.
+447836121121
3 Return to the home screen
Press the Home key to return to the home screen.