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.
There are four (4) ways to record your Voicemail Greeting in iPlum. A. Standard prerecorded voicemail greeting (Free) Note: This option is available both in iPlum app and online iPlum portal. The female voicemail greeting comes standard with all iPlum accounts. B. Record voicemail greeting in your own voice (Free)

iPhoneAlley details a technique to trick the iPhone into using any custom audio file as your voicemail greeting.
You can view and manage the greeting in Greeting Management.