Sometimes after flashing feature phones, the phone ends up with imei loss and shows null or invalid imei when you dial *#06#. Thus device has no network service.
This is a short tutorial which will show you how to restore the imei on feature phones using SN Write Tool.
Learn how to flash feature phones from here
Changing of imei is illegal. Use original imei found at back of the phone.
romkingz is not responsible for any damage caused using this tutorial
Do this at your own risk
Download sn write tool from here
Download and install feature phone drivers from here
Extract and launch SN Writer.exe
ComPort select USB VCOM
Target Type select Feature Phone
Click System Config
Under Write Options, tick IMEI
Under IMEI Option, tick Dual IMEI if you want to restore for both SIMs
Click MD1_DB and select the database file (Found inside stock ROM of the device)
Click SAVE to exit System Config
Click START button
Enter the IMEI numbers and click OK
When you see message showing wait for USB insert,
Connect phone to PC
When a message PASS in green is seen, process is complete.
Insert battery and reboot phone.