Sprint announced last year that it would begin slowing speeds for its heaviest data users, saying those customers "consume a disproportionate share of network resources and cause a negative user experience for the rest." The change intermittently affected speeds for the top 5 percent of data users, Sprint said.

Although in the past the FCC has stepped in to stop internet providers from slowing speeds, the Commission's new rules also cover mobile for the first time. Sprint told the Journal that, although it stopped the practice, the company believes the throttling was allowed under the rules.

Meanwhile, the FCC is still facing down industry lawsuits over the rules. A judge declined a request to stop the rules from coming into effect, but oral arguments are expected to begin around the end of the year.