Getting around a BAN

i was wondering I has cable modem and was wondering how I change IP address on it from my computer which is 2 routers away from main connection or do I just change the IP for my PC

Inform the first router (the one connected to the internet), that you wish to reconnect. If you have admin or at least user access, you should be able to do this via the web interface, else you might try UPnP.