From another Ooma Office phone. Dial your internal extension number and wait for the call to roll to voicemail. Press [*] and enter your PIN. Select option 5 from the main voicemail menu. Select option 1 from the submenu to record a new greeting, or option 2 from the submenu to record a new name.
All sorts of funny issues can occur when your phone hasn’t had a reboot in a while. Rebooting allows your phone to clear out and fix any issues. So try switching it off for at least five minutes, then see if the problem is resolved.

Listen to and manage your U-verse Voicemail messages by phone or online. Dial *98 from your U-verse home phone, dial your home phone number from another phone, or access your voicemail messages online from the Voicemail Settings tab. Press the * key when you hear your greeting. Enter your PIN. Press 4 and follow the prompts.
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.