While visual voicemail is nice, I use a 3rd party voicemail system that works better for me thanks to some of its notification features.
With T-Mobile, I could easily set up my Busy/No Answer forwarding number through a menu on my phone, but I couldn't do that on the iPhone. So a little research got me this, which works.
QUERY YOUR CURRENT SETTINGS
First, check which number your voicemail is going to. Mine is 13059724650 which is the main AT&T voicemail system. I'm guessing that this is the same for everybody. But just to be sure, open your phone keypad and dial: *#61#
You'll get a bunch of text and the voicemail number towards the top. Write it down somewhere safe.
SET UP BUSY FORWARDING
**67*destination#
CANCEL BUSY FORWARDING
##67#
At this point you may want to set up busy forwarding again for your original voicemail number you obtained earlier so that you can use the visual voicemail again.
SET UP NO ANSWER FORWARDING
**61*destination*11*delay#
The delay is in 5 seconds increment with a maximum delay of 30 seconds
CANCEL NO ANSWER FORWARDING
##62*11#
At this point you may want to set up no answer forwarding again for your original voicemail number you obtained earlier so that you can use the visual voicemail again.
DISCLAIMER: This worked great for me but I take no responsibility if you break your set up performing the above steps. Use it at your own risk.
With T-Mobile, I could easily set up my Busy/No Answer forwarding number through a menu on my phone, but I couldn't do that on the iPhone. So a little research got me this, which works.
QUERY YOUR CURRENT SETTINGS
First, check which number your voicemail is going to. Mine is 13059724650 which is the main AT&T voicemail system. I'm guessing that this is the same for everybody. But just to be sure, open your phone keypad and dial: *#61#
You'll get a bunch of text and the voicemail number towards the top. Write it down somewhere safe.
SET UP BUSY FORWARDING
**67*destination#
CANCEL BUSY FORWARDING
##67#
At this point you may want to set up busy forwarding again for your original voicemail number you obtained earlier so that you can use the visual voicemail again.
SET UP NO ANSWER FORWARDING
**61*destination*11*delay#
The delay is in 5 seconds increment with a maximum delay of 30 seconds
CANCEL NO ANSWER FORWARDING
##62*11#
At this point you may want to set up no answer forwarding again for your original voicemail number you obtained earlier so that you can use the visual voicemail again.
DISCLAIMER: This worked great for me but I take no responsibility if you break your set up performing the above steps. Use it at your own risk.