To update the Carrier settings and iPhone, a Wi-Fi connection is mandatory. Open the Settings app > General > Software Update, this will help you update the iPhone.
.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.

Hello, it’s obvious you have bad timing, because nobody is home. Please leave your name, telephone number, and a brief message in a voice similar to mine, and your call will be returned as soon as humanly possible.
There you have it, a basic introduction into how to write the best voicemail greetings. As you have seen, they’re not as easy as you’d think, but once you get comfortable with the type of information required by each, writing and recording your own should be a piece of cake. If you’ve tried to write one yourself and still don’t ‘feel you’ve captured the right essence, then please look at one of our voicemails greeting templates. When it comes to recording it, remember to rehearse your script and speak clearly. If you don’t care for your own voice, then have someone else record it, or hire a professional voice actor. Remember, there are also free audio editing software programs like Audacity, where you can manipulate your recording until you get exactly what you want.