Google systematically blocks calls to certain areas from consumers using Google Voice, AT&T said, citing press reports. By doing this, Google can reduce its access expenses, according to AT&T. The FCC in 2007 prohibited traditional carriers from blocking calls because it said the practice might degrade the reliability of telecommunications networks, Quinn wrote.

AT&T charges that Google's call blocking violates the fourth principle of the FCC's Internet Policy Statement, which says consumers should be able to reap the benefits of competition among network, application, service and content providers. Though Google has claimed that Google Voice is not a traditional phone service, it effectively is, AT&T says. And even if it's an application and not a phone service, Google Voice is still governed by that principle because it covers application providers, the letter said.

The carrier also accused Google of violating , on nondiscrimination, which says one provider can't block fair access to another. Google itself is discriminating when it blocks calls to certain local exchange carriers, AT&T said.