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?
We’ve heard frightening stories of people who have been hit by huge bills because of annoying marketing calls that went to voicemail, so that's something you really need to avoid, such as this article in the Telegraph.

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From another phone, call your own phone number. 2. Wait for the recorded "Please leave a message" greeting to start playing, then tap the pound key (#) on the phone's dial pad. 3. Enter your