Touch and hold the number 1 on the Keypad tab (lower-left) to activate it. If prompted, enter the voicemail password and then hit the # key to continue. What is the procedure for setting up voicemail on my Samsung? Configuration of Android VoicemailTo access the settings menu, click on the three dots in the upper right corner of the screen.Select “voicemail” from the drop-down menu.Select “Advanced settings” from the drop-down menu.Select “setup” from the drop-down menu.Select “voicemail number” from the drop-down menu.Enter your ten-digit phone number and press the “OK” button.To return to the main menu, press the home key on your keyboard. Is there a voicemail app available for Samsung?
Vivio help you to stay connected with this O2 Voicemail set-up guide on an Android OS Galaxy handset

However, some cellular service providers allow users to access and update their voicemail by calling their own numbers from working landlines or phones on other wireless networks, so users whose accounts include such an option and who have access to alternative service could keep the voicemail greetings updated even when their own mobile phones cannot connect to cellular or internet service.
Retrieving voicemail messages. Users can listen to voicemail messages by accessing Nextiva Voice mailbox from a Nextiva phone or external phone. If calling from the primary phone, dial *86, otherwise if calling from any external phone, dial the phone number and press the * key during the voicemail greeting.