Tap Voicemail, then tap Set Up Now. Create a voicemail password. Choose a greeting-Default or Custom; if you choose Custom, you can record a new greeting. See More...
To change or record your voicemail greeting: From your: Wireless phone: Press and hold 1 or the Voicemail key. AT&T Wireless Home Phone: Dial 1 from your connected home phone. Enter your voicemail password if prompted. In the Main Menu, press 4 for Personal Options. Press 3 to Change Greetings. Follow the voice prompts to record a personal

A professional voicemail greeting is a recording that informs clients and business partners you are not available to receive their call. It is an essential part of any effective business communication strategy, especially if you are in sales.
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.