Follow the link above if you want the simple VVM that comes free with LTE. If you use the messages app, it will deactivate the VVM from you account IF you already had it. I would recommending deleting the messages app then calling ATT to have them put the VVM back on your account, then install using the apk from GSLeon.
From a post I did on XDA:
Thank you to GSLEON3 for this link. The APK is on the first post of the thread.
http://forum.xda-developers.com/show....php?t=1452330
1. Open the file and send the apk to your phone. I did this by copying and pasting the apk from the zip file, saving it and emailing the file it to my phone from my computer.
2. I downloaded the apk from the email on my GNote, went to the My Files app on the GNote found the apk in the download folder. Click to install. (make sure unknown sources is checked in the applications setting prior to installing)
3. Once installed it will try to call your voicemail once you open the app. (since I already had this set up on my account for my skyrocket, I entered my password and it loaded all of my saved voicemails) I was able to add visual voicemail from manage my account on the website back when I got the skyrocket.
I had this app on my skyrocket, added it to my ATT and International GNotes and it works fine on all three.