Restore IMEI of Xiaomi MI4C Without Another Phone
What you need.


Download MTK Droid Root &amp; tools.
A Windows computer.
Have already set USB Debugging mode enabled on your device.
A USB cable.
Have setup ADB &amp; Fasboot on your PC.


Instructions. 


Connect your device to PC, then launch MTK Droid Root &amp; Tools.
Droid Root and Tools will detect your Android device.
If your device is detected, you will see its IMEI on the Phone Information tab on the droid root and tool interface.
Then find the Root button that's located on the lower right side of the interface.
Select Yes button if asked whether you wish to Root. You will see Root Shell Script Access.
Then you'll see a window box named Change IMEI, Backup/Restore, NVRAM.
Now replace the IMEI on the window box with the IMEI number from the rear side of your Android device.
Then choose Yes. Reboot your device for the changes to apply and finish.


I got the instructions from the following page; repair MTK IMEI, that page contains pictures to clearer its point.