Here is what ATT DSL says they are delivering ----
"2. AT&T High Speed Internet Service Description
The Service is composed of narrowband or broadband access to the Internet provided by AT&T. The Site, provided by AT&T and Yahoo!, is composed of a broad selection of on-line resources including email, communication tools, forums, shopping services, search services and personalized content and branded programming. Broadband access is provided in speed tiers of: (1) 200 Kbps to 768 Kbps downstream (not available for AT&T U-verse High Speed Internet service), (2) 769 Kbps to 1.5 Mbps downstream; (3) 1.56 Mbps to 3.0 Mbps downstream; (4) 3.1 Mbps to 6.0 Mbps downstream; and (5) 6.1 Mbps to 10.0 Mbps (available only with AT&T U-verse High Speed Internet service) (collectively “Service Capability Speeds”)."
I've read the rest and cannot find mention of file size limits.
Comcrap seems to be the leader in cheating their customers...