To use a different greeting you already recorded or switch back to the default greeting: On your Android device, open the Voice app . At the top left, tap Menu Settings. In the Voicemail section, tap Voicemail greeting. Next to the greeting you want to use, tap More Set as active.
Users lacking the option and means of accessing their voicemail accounts from landlines would not be able to keep their greetings updated in the absence of cellular and internet service.

Note: If necessary, delete an existing greeting (limit of 2 greetings) to make room for the new greeting: Tap the Menu key, tap Delete greetings, tap the check box next to the desired greeting, and then tap Delete. Tap the Record icon to record your greeting. Tap the Stop recording icon to stop recording. Start by tapping on the phone icon found at your iPhone’s home screen. Go to the setting section on your iPhone. Now, you can go to the keypad on your phone and then type the number #404 and then call so that you are able to turn off voicemail on iPhone. How do you delete your voicemail greeting on iPhone? Tap Voicemail, then tap a message. Do any of the following: Play the message: Tap . Messages are saved until you delete them or your carrier erases them. Share the message: Tap . Delete the message: Tap . Why can’t I change my greeting on my iPhone?
Once you click greeting, you can change it from default to custom and record your custom greeting. Press play to listen to it before saving it.