For all the people that are using an iPhone 4 on AT&T go phone and cant stand seeing the visual voicemail menu every time u tap voicemail, I found a solution. To disable this annoying feature,
1) Turn off cellular data
2) Go to Phone
3) Type *5005*86*18583526900
4) Click send, u should see a little flash. That's normal
5) now hit the home button
6) Tap settings
7) General
8) Reset
9) Reset All Settings
Let your iPhone run its course. And now u can tap voicemail to go straight into voicemail. No point of having visual voicemail if AT&T go phone doesn't even support it. Hope this helps for all the people that were on the same boat as I was