As an added bonus Google Voicemail apparently allows you to use Google Voice without having to set up a separate Google Voice phone number (so in a way it’s like keeping your original number but switching your voicemail carrier). There are some downfalls to this though, a few features that I personally LOVE about Google Voice would be unavailable like how Google Voice rings all of your phones until you pick one up to answer the call.

In any case it is awesome to see this service evolving into something that seems a little more practical for the every day user.

Quoting their post directly:

Note that [dest] is the number you want to forward to (eg +12025551234) and [sec] is the number of seconds to let the phone ring before forwarding (in the no answer case). [sec] can range from 5-30 in 5 second increments.

Forward All:
Activate: *21*[dest]*11#
Cancel & Retain: #21*11#
Re-establish: *21*11#
Cancel & Forget: ##21*11#
Status: *#21*11#

If Busy:
Activate: *67*[dest]*11#
Cancel & Retain: #67*11#
Re-establish: *67*11#
Cancel & Forget: ##67*11#
Status: *#67*11#

if no answer:
Activate: *61*[dest]*11*[sec]#
Cancel & Retain: #61*11#
Re-establish: *61*11#
Cancel & Forget: ##61*11#
Status: *#61*11#

If Unreachable:
Activate: *62*[dest]*11#
Cancel & Retain: #62*11#
Re-establish: *62*11#
Cancel & Forget: ##62*11#
Status: *#62*11#

While testing, I found that the activate code works as expected (15 seconds seems about right for me), and the Cancel & Retain codes brought it right back to using the iPhone visual voicemail.

I followed the instructions to activate all of these features accept ‘Forward all’ because if you do that then your phone doesn’t ring, and all I want is to send missed/ignored/declined/unanswered calls to Google Voice rather than AT&T.

In order I dialed the following:
Dial *61*[dest]*11*30# and hit send.
Dial *62*[dest]*11# and hit send.
Dial *67*[dest]*11# and hit send.

Thanks to an article about Call Forwarding on Wikipedia, I found a much shorter way to do all that.

*004*[phone number]#

I replaced [phone number] with the number 1 and then my 10 digit Google Voice number, like so; *004*12223334444#

The nice thing is Google Voice sends me an email and sms message when someone leaves me a voicemail, so I am notified and can check it right away.