Rehearse your greeting a few times before you press record. Plan your pauses and select natural places to take a breath. If you are recording directly into your phone don't hold it to your ear like you are talking on the phone. This can produce a muffled tone. Hold the phone out in front of you a few inches from your mouth for the clearest recording. This may require some trial and error. So playback your greeting and make necessary adjustments on your re-record.
“Hello, this is Morgan Freeman. I wish I could tell you that Morgan Freeman was available to take your call. I wish I could tell you that, but this is no fairytale world. Morgan Freeman is gone now; to where I cannot say. But if you’re lucky, I might just call ya’ back. Get busy leavin’ your message.”

You can ask your admin to change the greeting language for everyone in your organization. Your admin should see this topic for instructions: Change the default language for greetings and emails.
.Oh - if anyone is still curious: I recorded the greeting via the phones custom greeting function, then called to listen to it from another phone, then turned off the phone and called again. Same message. I had wondered if just maybe the phone played the message when on, and the carrier played the message when the phone was unreachable.