Here comes the bad news: I have a few complaints about the app, most of which could ultimately be resolved in a software update. The first is the voices, as I’ve already said. Secondly, the app UI isn’t all that smooth. I found myself tapping buttons three or four times before I got a response, and that was over a pretty solid WiFi connection. Luckily, little stuff like that can be fixed in an update, and we hope that the folks at Orange Vallée get that cleaned up soon.
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.

“Hi, you know who you called; leave a message, maybe they’ll call you back. Then again, maybe they won’t. That’s how life is. Point is, you’ve done what you can. Have a nice day.”
You may wish to record a personalized voicemail greeting on your Intermedia phone. For detailed instructions click on the specific phone model.