If you still remember the password of voicemail on iPhone, you can easily change the password of your voicemail on iPhone. When you forget the voicemail password, you should retrieve the information from the Email or call the carrier directly for a solution.
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?

When using a Cisco phone, you can record and change your voicemail greeting directly on the phone. For the following instructions, to select an option, you can use the phone's blue toggle button to scroll down and highlight the desired option, and then press the Select soft key. Press the Services (globe icon) button on the phone.
Thank you so much! I have Metro PCS and an Iphone 5S. I called my carrier and reset my VPN and now I can retrieve my voicemail. Yippie!!!!!