When you get a voicemail, you can check your message from the notification on your phone. Swipe down from the top of the screen. Tap Voicemail ….You can call your voicemail service to check your messages. Open your device’s Phone app . At the bottom, tap Dialpad . Touch and hold 1. How do you listen to your voicemail from a different phone? Call your 10-digit wireless number. When you hear your voicemail greeting, press the * key to interrupt it. If you reach the main voicemail system greeting, enter your 10-digit wireless phone number, then interrupt your greeting by pressing the * key. Can I listen to my voicemail without setting it up?
The telephone systems have the feature named as Voicemail. VoIP is the best example of it. When a receiver is unable to pick up the phone, then the caller can leave the voice message on the receiver’s phone. In older telephonic machines, such messages were stored as a voice message directly, and the receiver can hear them later. In modern telephone systems, such info is being stored on the server of the service provider in the user’s mailbox. It is similar to email in which the messages are saved in the form of audio instead of text.

Website: https://www.att.com/support/smallbusiness/article/smb-wireless/KM1009187/
It's in the upper right corner of the screen. Then you have to re-enter the new password. Please be careful, you need to enter it exactly as you did the first time. Or else, you have to reset the password.