To view the current IMEI and technical details of your Nokia TA-1139, use these standard codes: View IMEI:
In some regions, third-party technicians use "Engineer Mode" codes to repair invalid IMEIs. While these vary by firmware version, common codes reported by community members on and forums for HMD Global (Nokia) feature phones include: *#*#3646633#*#* (General Android/MTK Engineer Mode) 3. Legal and Technical Warnings
That being said, here's a general outline of the steps involved in changing the IMEI on Nokia TA-1139: