i dont remember much from my cisco classes that i took 10 years ago but i think it depends if they banned your ip or your mac address. if they banned your ip, you might be able to request your internet provider to change it, if they banned your mac, i dont think there is much you can do unless you mask your mac
found this on google http://www.a3webtech.com/index.php/get-around-a-website-ban.html