*#06# -Displays the 15 digit IMEI (International Mobile Equipment Identity) in the middle of the screen. (This number is also printed on the back of the iPhone.)
Write this number down. You can provide this to your carrier to deactivate the phone, no SIM card will work -if ever lost or stolen.
*#21# -Displays 'forwarding' state (enabled or disabled) voice call, data, fax, SMS, sync data, Async data, packet access, and pad access forwarding for outgoing calls.
*#30# -Displays 'Caller ID' (enabled or disabled).
*#33# -Displays 'barring' state (enabled or disabled) voice call, data, fax, SMS, sync data, Async data, packet access, and pad access forwarding for outgoing calls.
*#43# -Displays 'call waiting' state (enabled or disabled) voice call, data, fax, SMS, sync data, Async data, packet access, and pad access forwarding for outgoing calls.
*#61# -Displays 'call forwarding to voicemail' state (enabled or disabled) [and number forwarded to] of voice call, data, fax, SMS, sync data, Async data, packet access, and pad access forwarding for outgoing calls.
To change the number of seconds before the call forwards to voicemail, retrieve your eleven digit number from *#61# then carefully type *61*numberRetrieved*11*30# -those last two digits are the seconds to ring (Default is 20; Max = 30)
*#62# -Displays 'call forwarding when unreachable' state (enabled or disabled) [and number forwarded to] of voice call, data, fax, SMS, sync data, Async data, packet access, and pad access forwarding for outgoing calls.
*#67# -Displays 'call forwarding when busy' state (enabled or disabled) [and number forwarded to] of voice call, data, fax, SMS, sync data, Async data, packet access, and pad access forwarding for outgoing calls.
*225# -Requests an SMS message displaying the current monthly balance. (if applicable)
*646# -Requests an SMS message displaying the remaining monthly minutes. (if applicable)
*777# -Requests an SMS message displaying the pre-paid account balance. (if applicable)
*3001#12345#* -Displays 'Field Test Mode', network, cell, GPRS, call, and version information.
Please note that *#4720# (voice quality reduction codec -to save battery) and *3370# (better voice quality codec) do not currently work on the iPhone.
** at&t as in sbc. (NOT to be confused with the original AT&T, which was a decent company.)
