Download and extract SN Write Tool On Your PC.After U Will See Following Files (Look Image Below) Now Run SN Writer.exe As Administrator.
After open SN Writer.exe U Will See The Following Screen (See Image Below)
Now Select On ComPort: and Select USB VCOM and Also Click On Target Type: and Select Smart Phone (only for android phones, if u want to write IMEI on feature phones then select feature phone option as target type )
Now Click On "System Config" Button
Once System Config Is Launched Then Choose IMEI in Write Option (U Can Also Select BT & WiFi Option )
If U Have Dual SIM Phone Then Select Dual IMEI (if u have single sim phone then skip this step)
Now Add MD1_DB and AP_DB Under DataBase File Option (Both Files Come With Your Phone Firmware) and After Click On Save Button.
Now Click On Start Button
Now Write IMEI Here and Press Ok
After Connect Your Switched OFF Phone Through USB Cable and Wait For Complete.
After Complete U Will See Green Pass :)
Warning: IMEI Changing Is Illegal. This Tool Is Only For Repairing Orignal IMEI ( Orignal IMEI Can Be Found In Back Sticker Of Phone ).
Credits: This Tool Is Created By Mediatek Inc, Full Credits Goes To Them For This Wonderful Tool