T-Mobile US said it won’t drop a claim it runs the “fastest” mobile network in the country despite a recommendation from an advertising watchdog for it to do so.

The Better Business Bureau determined T-Mobile should drop the speed claims from adverts, along with an assertion its network is “newer” than Verizon’s. According to the bureau, T-Mobile’s claims were based on unreliable crowdsourced data from Ookla and OpenSignal. The recommendation came from the bureau’s National Advertising Division (NAD) in response to a complaint filed by Verizon earlier this year.

NAD is responsible for reviewing US adverts for truthfulness and accuracy.

While T-Mobile initially agreed to comply with NAD’s suggestions, the operator reversed course after stating it found additional NAD-recognised evidence to back up its speed claim.

In a statement, T-Mobile’s SVP of Corporate Communications Janice V. Kapner explained: “On the fastest LTE network challenge, NAD ruled that the one month of crowd-sourced data we submitted (when Verizon launched their unlimited plan) could not be used. NAD previously recognized third-party crowd-sourced data as a way to look at network performance, so we looked at the latest results, and verified what we already knew.”

“T-Mobile is still the fastest LTE network and we’ll continue to let consumers know that!”

Data bias
In its original complaint, Verizon accused its rival of “cherry picking” data and otherwise misrepresenting itself in advertising. Specifically, Verizon challenged T-Mobile’s much-touted claim regarding data rates and a declaration Verizon’s network is aging, and was, by implication, somehow worse than T-Mobile’s network.

According to NAD’s review, T-Mobile’s reliance on crowdsourced data from Ookla and OpenSignal speed tests was flawed.

Verizon argued the speed tests could have oversampled Verizon customers who saw their speeds deprioritised, and thus misrepresented T-Mobile’s comparative speed. NAD agreed, concluding the Ookla and OpenSignal test results in the month after Verizon introduced unlimited plans might have been biased in favour of T-Mobile and did not adequately support the comparative claim it operates the faster network.

Prior to T-Mobile’s reversal, a Verizon company representative said the operator was “pleased, though not surprised” by NAD’s finding.

T-Mobile CEO John Legere (pictured) on Thursday (28 September) coined a new slogan, referring to T-Mobile as “America’s Best Unlimited Network,” citing Ookla figures.