AT&T mobile users are often behind carrier-grade NAT, so one public IP can represent thousands of phones, and geolocation may land on a regional gateway city rather than the user's location. AS20057 is used for some AT&T Mobility ranges.
Networks (ASN) / AS7018
AS7018 AT&T Services
Residential / mobile ISPUS
AT&T's core network covering fibre, DSL and much of its mobile traffic. One of the largest US consumer ASNs.