ATT INternet!!!!

what in the world!!1 i've been without internet at my house for sometime now. the problem was the modem so they sent us a new one in the mail. i hook it up and no internet still. when you hook it up it directs you to a WEBSITE!! AND YOU HAVE TO DOWNLOAD!!! SOFTWARE SO YOU CAN CONNECT TO THE INTERNET. you have to update your password to update the modem well it gets to the update and never updates still no internet!!! att has no idea what to do to fix it.