*#43#
Use to verify if call waiting is
enabled
*#61#
Verify the number for unanswered
calls
*#62#
Verify the number for call forwarding if no service is
available.
*#67#
Verify the
number for call forwarding if phone is busy
*#33#
To verify whether barring is
enabled or disabled for outgoing
*#21#
To display the settings for your
call forwarding
*3001#12345#*
Enters Field mode which allows you
to access most of the hidden settings and functions of your iPhone.
*#06#
Display the IMEI of your iPhone, as
always this is the standard code for all brands of phones.
*225#
Displays the account balance for postpaid contracts.
*777#
Displays the
account balance for prepaid
accounts.
*646#
Displays the remaining minutes
available.
*3282#
Get your data usage
information.
*729
Options to make payments. Its
operator specific.