By using the reset network settings, an effectiveoption to solve network related issues, you can fix allthese problems by simply resetting the networksettings of your iPhone as it will clear all the networksettings, current cellular network settings, saved Wi-Finetwork settings, Wi-Fi passwords, and VPNsettings How do you reset your voicemail greeting? From the Home screen, tap the Phone icon . Tap Voicemail then tap Greeting (upper-left). Greeting islocated in the top-left corner of screen. Tap Custom to record a greeting. Enabled when a checkmark ispresent. Tap Record to begin recording the custom greeting message. Tap Stop to end recording then tap Save. How do you change voicemail settings on iPhone? Go to the Phone app, then tap the Voicemail tab. Tap Set Up Now. Create a voicemail password, then tap Done. Enter your password again to confirm it, then tap Done. Select Custom or Default. If you choose Custom, you can recorda new greeting. Tap Done to save your greeting.
source: I have had the same voicemail greeting for 6you years and would like to change it. how do i change my voicemail greeting on my droid x2? thanx?

Set up voicemail on iPhone 11 is not a difficult thing, so you must have it. Through it, you will share voicemails with AirDrop. You can save them as an audio memo to save on space, mail them to others, and more. Let’s enjoy it and personalize it as you wish to get comfortable using the voicemail system.
Alternatively, you could try disabling call forwarding, though your particular carrier or phone model may not allow it: