How can I disable the voicemail button on iPhone?

You can disable voicemail button (not remove it) if you jailbreak and install "voicemailblock" from Cydia it will disable it. Works with SBSetting so you can enable and disable the button when you want.

I suspect that because the vast majority of people with iPhones do use voicemail, you're out of luck. Apple isn't known for providing settings or options that only a small percentage of users will want, especially if it's a setting that might prove confusing in the future.

Their UI designers likely weighed the number of users who don't want the button vs. the number of users who will be confused because their voicemail button is now missing and decided against the potential confusion. That certainly seems to be how they make most UI decisions.

*5005*86*XXX#

hit the CALL button after typing that code into the dial screen

Use this to reset where the button dials

XXX can be blank (*5005*86*#) and it will throw an error when this is pressed, or you can put another number in there to make a quick dial to someone else such as a phonecard.

Confirmed working on iOS 4.3