You definitely need to give more information. I don't have uverse boradband, butI can guess how they are setup.
Generally as you know the internets is a series of tubes connecting one device to another.
In your case, your internets tube comes from the ATT glass to a distribution point in your neighborhood and is then piped into your home through a metal cable. You need to have something that converts the information cars from what they are in the internets tubes to something your device can read, so you have (usually) a modem that sits in a pretty box connected directly to the metal wire ATT tube. I'm not sure if they use twisted pair cable or coax, but when they installed it, they likely hooked up a wire the their friendly box.
Here's where it gets tricky. Once the data cars reach the modem, you need to share them to your PC with either another tube that you install (like a cat 5 cable for LAN) or the modem will switch the traffic for you to a wireless flight path that then connects to your PC.
So you need to know if you have wireless (WiFi) or Wired (LAN) connections to your router/router. and it would be good to know if it's a router or a straight modem. usually routers have both Wifi and LAN connections, so you should see another cat 5 cable coming out of the modem that plugs into your PC.
I will stop here. If you have a more complex setup with more switches and routers etc...then you should start your troubleshooting by taking those added bits out of the path. Connect your PC directly to the ATT box and reboot everything. You should then get internet access. If not give us more information.