Go to the Phone app.Tap on the “Voicemail” tab at the bottom right.Tap “Set Up Now”.Now create a voicemail password and then select “Done”.Re-enter the voicemail password again and then select “Done”.Select the custom or default option for your Voicemail. If you wish to record your own Voicemail, select “Custom”.Voicemail should now be set on your iPhone 12 device.
I have a confession to make: I haven't recorded a new voicemail greeting in nearly a decade. Since then, I've (hopefully) become more articulate, poised, and self-assured. But hear my voicemail recording, and you'd think I was still new to the work world, a little unsure of myself — and probably not an authority.

6. Full Waiting Queue Message. What the caller hears when the waiting queue is full. Sample Scripts: “We are currently experiencing high call volume. Please leave a message with your name and phone number and we will return your call as soon as possible.”
If your carrier supports the iPhone voicemail feature, you can retrieve and listen to your voicemail right from within the “Phone” app and call your contacts back by simply tapping their messages. That type of functionality is pretty neat and useful, because it saves you actual time. If not supported by your carrier, you will not be able to see the visual overview of your voicemail inbox and use any of the related features. Tapping the “Voicemail” tab in your “Phone” app will simply call the number associated with your voicemail box. So let’s get going with creating our custom voicemail greeting on iPhone! How to record your own Voicemail on iPhone Phone → Voicemail → Greeting → Custom → Record → Save