Entering incorrect codes or messing with Engineering Mode settings can permanently disable your device's cellular functions. Official Solutions:
Modifying an IMEI is strictly illegal under the Mobile Telephones (Re-programming) Act 2002 unless you have the manufacturer's permission. q106 imei change code
If the direct codes don't work, technicians often use the menu within the Engineer Mode to manually send AT commands: Open Engineer Mode: Dial *#*#3646633#*#* . Entering incorrect codes or messing with Engineering Mode