Hey babujbf, I know you can change the internal IP address easy enough, but if you're behind a router (or even ethernet I believe) you'd want to change your external IP address to get around the ban (since thats what they have on you anyway) and I think you'd need to contact your ISP for that.
To see if the two IP's are indeed different (internal vs external) you can compare the output of ifconfig in a terminal to what a site like:
http://www.whatismyip.com/ says your external IP address is.