Nokia Codes might find helpful:

1. Type*#06# for checking the IMEI (International Mobile Equipment Identity).
2. *#7780# reset to factory settings.
3. *#67705646# This will clear the LCD display (operator logo).
4. *#0000# To view software version.
5. *#2820# Bluetooth device address.
6. *#746025625# Sim clock allowed status.
7. #pw+1234567890+1# Shows if sim have restrictions.
8. *#92702689# - takes you to a secret menu
9. *#3370# - Enhanced Full Rate Codec (EFR) activation. Increase signal strength, better signal reception. It also help if u want to use GPRS and the service is not responding or too slow. Phone battery will drain faster though.
10. *#3370* - (EFR) deactivation. Phone will automatically restart. Increase battery life by 30% because phone receives less signal from network.
11. *#4720# - Half Rate Codec activation.
12. *#4720* - Half Rate Codec deactivation. The phone will automatically restart (If you forgot wallet code for Nokia S60 phone, use this code reset)
13. *#7370925538# Your data in the wallet will be erased. Phone will ask you the lock code. Default lock code is: 12345