T-Mobile CEO John Legere is, as he would likely say, pissed off.

This week, leading digital-rights advocacy group the Electronic Frontier Foundation released tests showing that T-Mobile’s Binge On feature throttles streamed video. Now, Legere has taken to Twitter to ask, “Who the fuck are you, anyway, EFF?”

T Mobile’s Binge On program allows customers to stream video without reducing their allotted data limit. What T-Mobile doesn’t tell customers—at least not in clear language—is that the speed and quality of those videos are significantly reduced.

Jeremy Gillula, the staff technologist at the EFF who ran the test, says his interest in the Binge On program was peaked when he saw articles saying the program was throttling video.

“That was when I was curious,” Gillula told the Daily Dot in a phone interview. “I was like ‘Well, let’s see if that’s true.’ I’ve seen some allegations, but I can test that. More than anything it was me being a geeky computer science nerd, curious about what was going on. Admittedly, I did have a concern about net neutrality and customers being able to make choices, and more importantly, informed choices.”

Gillula uploaded a video to a server and tested the connection on a T-Mobile phone with Binge On enabled and one without. The results are telling.

Electronic Frontier Foundation

T-Mobile says they’re merely “optimizing” video, but it seems like another word for throttling, according to the EFF. “That’s the way it seems to me,” Gillula said. “From a technical perspective, I cannot square the word optimization with the practices we saw. When they actually talk about the details of practice, I can’t square the details with the idea they’re doing any optimization.”

“It seems to me like they’re throttling to a speed which would correspond to a DVD video and then hoping that whoever is serving the video would do the optimization to bring the bitrate down to DVD quality,” Gillula told the Daily Dot.

Regardless he said, T-Mobile is throttling the video of all Binge On customers down to a certain quality.

Legere did not respond to our request for comment.

The EFF is not against Binge On. Gillula said it just needs a few “simple tweaks.” One of the biggest problems is that the program is enabled by default, so users don’t get to decide if their video data is throttled unless they actively turn it off.

The next step, Gillula says, is for the Federal Communications Commission to investigate the issue.

“It basically comes down to the fact that it seems to us this practice isn’t necessarily neutral,” Gillula said. “What we found in the [tests] is different from what they’ve been saying publicly, but when we asked them directly, they confirmed what we say in the blog post.”

“It seems like there was a lot of confusion,” Gillula said. “And in some sense an FCC investigation would help clear up a lot of the confusion and get a straight answer for T-Mobile.”

Illustration by Max Fleishman