Phrack 48 has an excellent article on Modify the ESN of Radio Shack / Nokia cellular phones by Damien Thorn.
On many Nokia and Radio Shack phones, to find the security code (Neccessary for NAM programming), enter ##591463275 Sel 9. The security code is displayed on the phone.
Nokia's home page
© 1994-1996 Copyright Sinister Networks. All rights
reserved. May not be redistributed or modified without permission of
Sinister Networks. Do not fold, spindle, or mutilate. Fnord.
Other names and marks used in here are the property of their respective
owners, until and unless decided otherwise in a valid court of law. The
absence of a service mark,
trademark symbol or fnordmark in connection with the marks identifying
products or services of other vendors does not indicate
the absence of registration of those marks or devices. All marks identified
herein are used or registered in the United States of
America and may or may not be used and/or registered in other countries
and planets.