There are two steps you have to do before you can use voicemail on your phone. The first is that you have to add a voicemail number. This number varies by country and also your service provider. If you’e use AT&T, you can follow AT&T Galaxy S21 voicemail setting. Open the “Phone” app. Tap the 3 dots on the top right. Tap “Settings“. Tap “Voicemail“. Tap “Voicemail Settings“. Take note of the green number below “Voicemail number“. Go back to the dialer and enter the number from Step 6 (including the *). Press the green phone button. The voicemail number has been set. Return to the Start screen.
How do I listen to my own voicemail greeting on iPhone?How do I turn off voicemail? Looking in the voicemail settings and searching for a ‘Deactivate‘ or ‘Turn Off‘ option is an obvious first step regardless of the phone you’re using. If you find the correct option, disabling it will turn off the voicemail function.

Last, make sure you keep this voicemail account up to date, especially if you have some kind of "out of office" message, telling people where you are. Michael Hyatt updates his voicemail message every day-- it may seem excessive, but it lets his callers know that he regularly checks his voicemail, cares about messages he receives, and is likely to get back to them.
Shared voicemail and call routing is intended for multiple access and directing calls to one or multiple phones. Mobile apps are also available that allow you to check your messages from your phone. The below infographic outlines the current state and trends of voicemails.