Federal regulators are looking into new offerings, such as T-Mobile's Binge On, that exempt video and other services from data caps to determine whether they violate new rules for Internet traffic.
Tom Wheeler, chairman of the Federal Communications Commission, said Thursday the agency sent letters to T-Mobile, AT&T and Comcast asking for informal meetings to discuss "some of the innovative things they are doing."
"This is not an investigation. This is not any enforcement," he told reporters after the agency's monthly meeting.
The letters were sent Wednesday, and the companies were asked to make employees available by Jan. 15.
Wheeler said the goal is for FCC officials to stay aware of innovative services in the wake of the agency's tough new net-neutrality regulations, which are designed to ensure the uninhibited flow of Internet content.
Those controversial rules, which took effect in June and are being challenged in court, prohibit Internet service providers from discriminating against legal content flowing through their networks.
Some consumer advocates and other critics have raised concerns about so-called zero-rating and sponsored-data plans, which exempt select content from counting against customer data limits.
Such plans could hinder innovation by giving preference to certain content providers.
Binge On was unveiled last month with great fanfare by T-Mobile Chief Executive John Legere at the Shrine Auditorium in Los Angeles. The service allows customers to watch as much video on their mobile devices as they want from Netflix, Hulu, HBO, ESPN and about 20 other providers.
"We want to ensure that we have all the facts to understand how this service relates to the commission's goal of maintaining a free and open Internet while incentivizing investment and innovation from all sources," Roger Sherman, chief of the FCC's Wireless Telecommunications Bureau, wrote to T-Mobile.
T-Mobile said it looked forward to giving the FCC details about Binge On.
"We continue to be strong supporters of net neutrality and firmly believe in the principles of equal access to an open and free-flowing Internet," the company said. "This program provides both great customer choice and industry innovation that encourages competition, and we believe it is absolutely in line with net-neutrality rules."
Similar letters were sent to AT&T about its Sponsored Data and Data Perks plans, which allow companies to subsidize the data costs for customers using their services, and to Comcast about a new offering called Stream TV.
Now being tested in a handful of markets, Stream TV allows the company's Xfinity Internet customers to stream Comcast cable programming that doesn't count against data caps.
"Our Stream TV service does not go over the public Internet . It is a cable service that only works in the customer's home," said Comcast spokeswoman Sena Fitzmaurice. "It is not a so-called 'zero-rated' service."
Comcast would participate "in the FCC's fact-gathering process relating to industry practices," she said.
AT&T said it was reviewing the letter and would respond "as appropriate."
"We remain committed to innovation without permission and hope the FCC is too," AT&T spokesman Michael Balmoris said.
The meetings will be an "informal review of new offerings so the commission is fully informed about new marketplace offerings," FCC spokeswoman Kim Hart said.
The companies also can discuss "their views on how the broadband industry as a whole is developing," and the FCC "will invite others — including other commercial interests and public-interest groups — to meet with us as well," Hart said.
The net-neutrality rules were passed on a partisan vote by Wheeler and the FCC's other two Democratic members.
The agency's two Republicans, who opposed the rules, complained Thursday that they had not been told of the letters and said Wheeler was on a "fishing expedition" for net-neutrality violations.
"Make no mistake, this is an investigation," Commissioner Ajit Pai said. "This is not simply a benign informational inquiry."
Hart said all commissioners' offices were told about the letters before they were sent and received copies Thursday.