How to turn off voicemail on iPhone 4s?

My service provider is 3. Will it cost money to turn off voicemail? Will it show up on the bill?

Instructions
1
Discover the number of your voice mailbox. Type "*#61#" without quotes and press "Call," then write down the number the service gives you.

2
Forward calls to the voice mailbox number. Go to "Settings | Phone | Call Forwarding." Set the voice mailbox number as the number to which calls are forwarded.

3
Disable the voice mail. Type "#004#" without quotes and press "Call." This should deactivate your voice-mail service. You can also choose to forward calls to a different number than the voice mailbox, or selectively enable and disable diverts for "no answer" (type "#61#" without quotes and "Call"), not reachable ("62" without quotes), or busy ("67" without quotes).

4
Reactivate voice mail:

Reactivate voice mail by dialing "*004#"" without quotes and pressing "Call."

5
Call AT&T customer support and request that they deactivate your voice-mail service if you need help doing this.