These are step by step instructions how to change your iPhone
IMEI easily! You can only do this with a 4.6 BL iPhone.
ZiPhone is capable of the following functions:
- Unlock and Imei changer will work ONLY on 4.6 BL (112
and 113 ootb).
- Jailbreak will work on any OS version.
- Activation will work on any OS version, except for youtube
on 1.0.X.
Perform these steps with your iPhone on and connected to your
computer.

Step One

Download ZiPhone here



Step two

Double click ZiPhone.zip on your desktop to extract the folder
ZiPhone.




Step Three

Press the Windows key and R at the same time to bring up the
Run window. Type in cmd and press the Ok button to launch
the Command Prompt.




Step Four

Type the following command into the Command Prompt to
navigate to the ZiPhone directory:
cd Desktop/ZiPhone.




Step Five

Execute the command ziphone to see all its possible uses.




Step six
The program will prompt you to put your iPhone into recovery
mode. To do this please hold down both the Sleep/Wake and
Power buttons until you see the Apple logo. Once the Apple logo
appears release only the Sleep/Wake button until you see the
iTunes logo and cable on the screen.



Step Seven
If you have a 4.6 BL iPhone you can now activate, jailbreak,
and unlock! Just simply type in this command:
ziphone -u -i a123456789012345
(Replace the numbers with the desired IMEI of your choice)




Step eight
The program will now search for zibri.dat. Then it will search
for the iPhone. Once found it will tell you to wait for 2 minutes
and 30 seconds.




Step nine
After this time your iPhone will reboot and it will be unlocked
with the new IMEI!!!

all these things

The best IMEI changer that you can get it for free on internet is from this page : http://www.unlockphonetool.com/how-to-change-imei-number/

chai,all these to change imei?na by force,android all the way especially the versions with mtk processors.