Select “1” for default voicemail greeting or “2” for a temporary or vacation voicemail greeting. If a file is selected here it will supersede the Media file (number 1 above). Once this is set back to None the Media file will play.
If you want to change the default voicemail greeting on your mailbox you will have 2 options.

Once installing InstaVoice, you can easily manage missed calls and voicemails in a chat-like interface. It helps you find out who called you or who left voicemails when your phone is switched off. You can read the voicemails and reply to them quietly, thanks to the voicemail transcription feature. InstaVoice keeps your privacy because you don’t need to listen to one mail after another.
Whether it’s an out-of-stock product, a canceled event, or social media snafu, there are times when your business may see an influx of frustrated callers. While it is important to address their concerns head-on, you may not be able to answer each call as it’s received. Make sure you use best practices for dealing with angry customers, and that your voicemail greeting sets the appropriate tone. Avoid defensive language, validate their concerns, and keep them informed as to how you are handling the situation.