Default Must retain DATA in ROM flash

I've bought a software and the stupid company has a policy that if you do a factory reset you loose access to the paid program. simple as that. I have argued that it makes no sense, since its the same phone, same imei, same number, just did a system uprade but they refuse to help. I did a nandroid backup, so what I want to ask is: is it possible to retain DATA after flashing a newer ROM over the original? so that the program would recognize the phone as the same and don't lock?