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?
5 hours agoTo change your voicemail message on iPhone: 1. On your home screen, tap Phone. Tap the Phone icon on your home screen to launch your device’s phone calling app. 2. At the bottom, tap Voicemail on the menu bar. You will see a menu bar appear at the bottom of your screen. Tap Voicemail in the bottom right corner. 3. Tap Greeting in the top left

Website: https://support.8x8.com/express/devices/voip-phones-headsets/8x8-express-how-to-create-or-change-outgoing-voicemail-message
The process is very simple. You'll just have to click the green phone icon, the same place you make calls, and navigate to the voicemail screen. On the voicemail screen, you'll see a greetings option on the top left.