Call your home phone number. Press # to interrupt the greeting, and then enter your PIN. Follow the prompts to listen to your messages. (Note: In some areas, the # key will not interrupt the greeting. Try pressing * or 2 instead.)
Just ensure that your voicemail set up within 60 days, or else, it will be removed from your account. Just click the "Phone" App from the home screen of iPhone. You can press "1" or the "Voicemail" key to access to voicemail on AT&T phone.

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?
4. If you're asked for a password, type in your password using the keypad. If you haven't created a password before, type your phone number's last four digits.