If you’re using AT&T for only Internet access (DSL), you still need your home phone wiring (or at least one location in the home where the phone service is still available) since that’s where the Internet service is delivered. With Internet only service, it just means you can’t use it for phone calls. But you still need the phone lines. You connect your DSL modem+router via its RJ11 port to the phone service/line in your home. Now you have Internet access at that modem+router. If you want to run Ethernet cabling throughout the home, you need to run that SEPARATELY. Then run an ethernet cable from one of the router’s LAN ports to the RJ45 port on the wall to provide Internet access throughout your home.