To change your Standard Voicemail greeting follow the directions below. Enter your password and the press # key. From Shoretel Communicator (You will need to have access to your Shoretel phone to record the message) In the menu bar, click More, then Prefereces. Your phone will turn on and beep. Begin your message.
4. To delete multiple voicemails, select and hold the first voicemail, then click on “More items.”

Hopefully, you found the interesting tips over here, to set different voicemail greetings messages on your iPhone that using Carrier like Verizon, AT&T, Sprint, T-Mobile and any other.
Follow the instructions and press that number. You will be asked to delete your current Voicemail greeting. Click on the ‘Yes’ button that appears on the screen if you want to remove that. You can save your new recorded Voicemail greeting or can use the default recorded option. From the home screen, select the Phone app. Note: Alternately, you can set up voicemail by selecting the Phone app then selecting and holding the 1 key. Select Keypad, then select the Visual Voicemail icon. Select Start. Select Ok. From any Home screen, tap the Menu key. Tap Settings. Tap Call settings. Tap Voicemail. Tap Voicemail again. View the voicemail number. Press and hold the 1 on your device’s dial pad to call and connect to your voicemail. Press the star * key to access the main menu. Press 4 to access the mailbox options. Press 7 to change the language of the voicemail prompts to either Spanish or English.