I have a 2wire router from AT&T and I cannot
I've never had any restrictions, I have an internal router, and several computers and devices access the internet through my AT&T account both wired and wireless. I don't know anything that would prohibit you using a machine to connect to the internet through one of their routers, and the fact that it can connect locally, if by locally, you mean you can access other devices connected to the router, then as a network analyst, computer guru, the only thing that I can think that 'might' interfere is your IP address on your computer; but, that would restrict the other devices from connecting to the internet too, or the laptop but not both. But, to me it sounds odd that you have such an issue, it has to be the way the network is configured on your laptop. If you know, you can check this through the DOS or Power Shell on your laptop. I presume it's windows, at the prompt, if windows, just type
ipconfig /all <return> = C:\ipconfig<sp>/all<return>
to check your network card IP and mask settings for all devices that could connect to the internet. Perhaps your laptop is IPv4 and the AT&T is set to IPv6 only, something like that.