AT&T has spent a year railing about how awful it would be if the Federal Communications Commission applied common carrier rules to Internet service. It doesn't make sense "to take a regulatory framework developed for Ma Bell in the 1930s and make her great grandchildren, with technologies and options undreamed of eighty years ago, live under it," the company said last month just after the FCC voted to reclassify broadband providers as common carriers under Title II of the Communications Act.

Yet in an area where the Title II rules already apply (telephone service), AT&T now stands to get millions in refunds for network connection charges precisely because of the same rules that ban unjust and unreasonable charges for telecommunications services. The case hinges on the same "unjust and unreasonable" standard that's now being applied to broadband, and it shows that Title II can be a huge boon to companies like AT&T.

In a decision this week, the FCC pointed to its Title II authority when it ruled in AT&T's favor. The company had complained that Great Lakes Comnet (GLC) and Westphalia Telephone Company (WTC) of Michigan "billed AT&T for interstate access services under an unlawful tariff."

"We agree with AT&T," the FCC wrote. "We find that GLC violated the Commission’s Rules governing competitive local exchange carrier tariffs for interstate access services, and that the tariff therefore is unlawful. We also grant AT&T’s claim in Count III that WTC unlawfully billed for services prior to May 2013 that GLC provided."

The FCC will rule next on how much money AT&T should get because of this overcharging. AT&T sought a refund of $12 million and is trying to avoid paying another $4.3 million Westphalia and Great Lakes claim they are owed.

The FCC's ruling said it has authority to declare that AT&T was billed unlawfully because of Section 201(b) of the Communications Act. That's the part of Title II that says, "All charges, practices, classifications, and regulations for and in connection with such communication service, shall be just and reasonable, and any such charge, practice, classification, or regulation that is unjust or unreasonable is declared to be unlawful."

Internet service providers are angry that Section 201 will apply to the broadband service they offer consumers, claiming it amounts to rate regulation. The FCC won't be setting specific price caps or telling individual providers what they can charge in advance, but consumers will be able to complain that their broadband providers are charging unjust and unreasonable rates—just as AT&T did in this case.

The FCC's AT&T decision also pointed to authority from Title II's Section 203 (public display of charges) and Section 208 (complaints). AT&T's dispute of the charges said that "WTC could not properly bill for 83 miles of transport because the traffic crossed LATA [local access and transport area] boundaries, and WTC’s tariff provides that its access services must be provided within a single LATA," the FCC said. "In addition, AT&T complained that WTC improperly billed for tandem switching when GLC owned and operated the tandem switch."

This isn't the only instance of telecommunications providers benefiting from the same Title II rules they oppose. Verizon, also a bitter opponent of using Title II to regulate broadband, used its status as a common carrier for telephone service to build its fiber network, which carries both telephone and Internet traffic. In addition to using Title II to secure pole attachments and access to rights-of-way, Verizon got permission to raise its customers' phone rates to fund the fiber expansion.

AT&T has also tried to use its status as a telephone common carrier to defend its throttling of unlimited mobile data customers in a lawsuit filed by the Federal Trade Commission.

The FCC's Title II decision for broadband lays out net neutrality restrictions that prevent Internet providers like AT&T from blocking or discriminating against online traffic. These practices violate the Section 201 restrictions on unjust and unreasonable behavior, the FCC said.

Verizon sued the last time the FCC passed rules such as these, and it won its case because the FCC had opted not to use its Title II authority. The FCC solved that problem by reclassifying broadband this time around, but it will still likely face lawsuits.

AT&T last month detailed potential legal arguments against the FCC's decision, but it looks like trade groups representing Internet providers, rather than the providers themselves, will take the lead in suing the FCC.