On the main screen type

*#06# for checking the IMEI (International Mobile Equipment Identity).

*#7780# reset to factory settings.

*#67705646# This will clear the LCD display(operator logo).

*#0000# To view software version.

*#2820# Bluetooth device address.

*#746025625# Sim clock allowed status.

*#62209526# - Display the MAC address of the WLAN adapter. This is available only in the newer devices that supports WLAN like N80

#pw+1234567890+1# Shows if sim have restrictions.
*#92702689# - takes you to a secret menu where you may find some of the information below:

    * Displays Serial Number.

    * Displays the Month and Year of Manufacture

    * 3. Displays (if there) the date where the phone was purchased (MMYY)

    * 4. Displays the date of the last repair - if found (0000)

    * Shows life timer of phone (time passes since last start)

*#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.

*#3370* - (EFR) deactivation. Phone will automatically restart. Increase battery life by 30% because phone receives less signal from network.

*#4720# - Half Rate Codec activation.

*#4720* - Half Rate Codec deactivation. The phone will automatically restart

If you forgot wallet code for Nokia S60 phone, use this code reset: *#7370925538#
Note, your data in the wallet will be erased. Phone will ask you the lock code. Default lock code is: 12345

Press *#3925538# to delete the contents and code of wallet.

*#7328748263373738# resets security code.

Default security code is 12345

Unlock service provider: Insert sim, turn phone on and press vol up(arrow keys) for 3 seconds, should say pin code. Press C,then press * message should flash, press * again and 04*pin*pin*pin#
Change closed caller group (settings >security settings>user groups) to 00000 and your phone will sound the message tone when you are near a radar speed trap. Setting it to 500 will cause your phone 2 set off security alarms at shop exits, gr8 for practical jokes! (works with some of the Nokia phones.)

Press and hold "0" on the main screen to open wap browser.

Important! Some of these codes may not work.

All you need to do is click on the link below and enter into the calculator your imei number witch can be found on the back of the phone under the battery.
Once you enter this code it will then generate your master unlock code then all you need to do is enter this new code when you switch the phone on and it asks for the security code, this will then remove the current security code and reset the code to what it was when the phone was new.

There are various profiles on the phone menu especially on the new china twin sim phones.

Go to profiles icon/menu

Scroll down to power save menu

Customise it to your style e.g. removing the vibration when on ringtone, minimising the brightness and put on daytime keypad lights.

Activate the profile.

You will save power and always keep your phone off vibration unless you are in a meeting.