Did you know that you can set how many seconds the AT&T iPhone will ring before it goes to voice mail? Sure you could call customer service and have them do it for you. If you are the techie type though, you will want to do it yourself with these steps:
Note: Be very careful when performing these steps. If you mess something up, you will need to call your wireless provider to have it corrected. These steps will only work with the AT&T version of the iPhone.
1. Call this number: *#61#
2. Write down the voice mail access number that appears on the line that says Forwards to.
3. Now call: *61*[vm access number]*11*n#
Replace [vm access number] with your voice mail access number
Replace n with the number of seconds that should elapse before the call is sent to voice mail.
To type a plus sign, hold down 0 for two seconds.
When complete, you should see the following on your iPhone:
Setting Activation Succeeded
Voice Call Forwarding
You have successfully changed the amount of time the iPhone rings before going to voicemail.