If this data gets wiped (due to a failed firmware flash or software glitch), your phone becomes a Wi-Fi-only tablet.
In many countries, changing an IMEI number to something other than the original, manufacturer-assigned number is illegal. These tools should only be used to restore the original IMEI of your device.
Find a QCN file specific to your exact phone model.
Before we discuss the tools, we must understand the anatomy of the problem.