The listed "*3001#12345#" code is actually what we in the cellular industry refer to as the "Long programming code".
This code only actually functions (usefully) on TDMA and CDMA phones. The reason for this being that with both CDMA and TDMA phones, your number is registered on the network within terms of the serial code (ESN) of your phone, and thus the phone needs to be programmed with the SID, SOC, and various network programming necessary to your phone picking up the correct providers.
Which all operates entirely differently in the US than overseas.
Needless to say, most of this is held in the SIM card on GSM phones, and is programmed over the air, which means that there's no point in you screwing around with your phone (thank goodness) saving us poor bastards in tech support large amounts of time wondering what you've done to your phone this time.
The "short" programming code for Nokia CDMA and TDMA phones is *#6391#. This will bring up:
- The MDN, or phone number,
- (depending on how old the phone is) the MIN,
- The SID
- And the SOC.
Much of troubleshooting for TDMA or CDMA phones not functioning or picking up the network consists of doing a Dummy ESN Change and then doing the short programming to kick the phone through into the network, often with a Hard Power Cycle involved.