On the iPhone, go into voicemail and tap "Greeting". Record a few seconds of something and tap stop. Before you tap save, use iFuntastic or SFTP to navigate to /var/root/Library/Voicemail on your iPhone. You'll see a file called "Greeting. amr". This is the audio you just recorded. Delete that file and replace it with your custom message which should then be renamed to "Greeting.amr". Tap "Play" on the iPhone to verify your message works. If it plays, tap "Save" and your custom message will be uploaded to AT&T's servers.
As you can see by reading our article on how to write the best voicemail greetings, they’re a bit more complex than one might imagine. There are important elements that cannot be left out, as to do so could cost you valuable business contacts. We realize this, so have included a selection of more funny, professional, and personal greeting examples, in MS Word and PDF format. By using these voicemail greetings, you’ll be well on your way to craft a greeting that will be pleasant to hear, provide the correct information, as well as requesting the correct information.

Hi, this is [Name]. I’m not currently available at the moment, but I look forward to talking with you. Please leave your contact information, along with a short message, and I’ll make certain to return your call.
In this guide, we describe every detail on the functionality and configuration of the Yeastar P-Series PBX System.