Android phones can access voicemail by holding down the 1 key on the dial pad until the phone dials your 10-digit phone number. You will automatically connect to your mailbox and be prompted to enter your temporary password; this password is the last 4 digits of your phone number followed by the # key. Start the Google Voice app. Tap the three horizontal lines at the top left of the screen (sometimes called a hamburger menu), and then tap “Settings.” In the Voicemail section, tap “Voicemail greeting.” Tap “Record a greeting.” How do I access my voicemail? To call your voicemail on an Android phone, simply open your phone’s dial pad and hold your finger down on the “1” key. You can also call your voicemail from a different phone by calling your own number and tapping the pound key. How do you check your voicemail?
5. Switch on and switch off Airplane Mode. You can do this from either Settings or the Control Center. On iPhone X or later, swipe down from the top right of the screen (where the battery indicator is).

If you are unable to set up your voicemail through phone settings, then you can try setting it up through your carrier. Voicemail is related to your carrier and it is best to be done this way. This may not work for all kind of carriers. You can easily apply this method by following the steps below:
Just NowVisual Voicemail Visual Voice allows you to access your voicemail mailbox using the display menu of your phone rather than following spoken mailbox prompts. Press the Message button to use the Visual Mail Option. ***Note*** If you read your voicemail in your email it does not automatically mark it read in your voice inbox.