samsung a300 help pls

i have been given an a300 samsung mobile legally from my uncle who found his lost phone . since the imei has been blocked, i now own it and am curious how to alter the imei.
i know this is illegal but want to try and unlock/alter the imei but i am trying to gain more knowledge and understanding. i have no intention of doing this all the time just curious.
can anyone help or doe's anyone have any software for me to use and play around with, can the nos on the a300 be altered.

thanks

roy
(newbie trying to learn)