T-Mobile CEO John Legere hosts an episode of his "Slow Cooker." He tweeted a jab at AT&T on Monday over its 5G label. (Jason DeCrow/AP for T-Mobile)

T-Mobile never wastes an opportunity to roast the competition.

So it was only a matter of time before the wireless carrier tweaked AT&T over its decision to advertise its mobile data network as “5G E” on certain smartphones, replacing the old “LTE” symbol that most users are familiar with. The change is active in hundreds of markets nationwide and applies to AT&T customers using the Samsung Galaxy S8 Active, the LG V30 and the LG V40.

On Monday, T-Mobile tweeted a video showing a disembodied thumb applying a “9G” sticky note to one of its smartphones. The sticker covered up the label showing that the device was in fact connected to T-Mobile’s LTE network.

“Didn’t realize it was this easy, brb updating,” the tweet said.

T-Mobile chief executive John Legere joined in the ribbing Monday: “Does @ATT really think that customers would fall for their mountain of ‘5G E’ BS?!” Legere tweeted. “Their ‘5G E’ is just LTE-A.”

Verizon piled on Tuesday as well, publishing an open letter in major newspapers claiming that “when we say ‘5G,’ we mean 5G.”

"People need a clear, consistent and simple understanding of 5G so they are able to compare services, plans and products, without having to maneuver through marketing doublespeak or technical specifications,” Verizon said.

And Sprint’s chief technology officer, John Saw, said Tuesday in a statement that “AT&T is blatantly misleading consumers — 5G E is not real 5G."

The jabs from other carriers arguing that AT&T’s “5G E” isn’t true 5G is the latest salvo in a growing marketing war over next-generation mobile networks. And the result is a whole lot of confused consumers.

The real 5G, which stands for “fifth-generation,” is considered the successor to 4G LTE, and advocates say it can support mobile download speeds that are 100 times as fast as current technology. Proponents also highlight how its low-lag properties can enable new applications that need a constant connection, such as self-driving cars and remote medicine.

But what AT&T is rolling out now is what it calls 5G E — short for 5G Evolution.

“We’ve been hard at work laying the foundation for 5G with technologies like 5G Evolution, now available in over 400 markets,” AT&T said in a statement. “To let customers know when they’re connecting to a 5G Evolution tower, we’re rolling out a “5G E” indicator initially on a handful of 5G Evolution capable devices.”

Here’s how the company described the nuts and bolts of the upgrade in a blog post last year: “We’re upgrading cell towers with LTE Advanced features like 256 QAM, 4x4 MIMO, and 3-way carrier aggregation,” AT&T said. “These technologies serve as the runway to 5G by boosting the existing LTE network and priming it for the future of connectivity. We can enable faster speeds now, and upgrade to 5G when it’s ready.”

Those technical changes, along with the addition of more wireless airwaves to AT&T’s network, should mean a performance improvement for AT&T customers, according to Walt Piecyk, an industry analyst at BTIG. “The step function increase in spectrum being added to the network should result in AT&T subscribers experiencing notably faster speeds when the 5GE tag is showing on their device,” Piecyk said in a blog post Monday.

But just because it’s a speed boost doesn’t mean it’s “real 5G,” which could still be years away, Piecyk added.

The marketing battle comes as carriers race to field the first and best true 5G wireless network nationwide.

Last fall Verizon switched on a version of its 5G network but only as a substitute for in-home broadband. AT&T sought to claim another victory months later by switching on its mobile 5G network in some markets, but the only way to use it is through a dedicated mobile hot spot.

In both cases, each company sought to claim credit for achieving a “first” in 5G. But despite the hype, it will probably take years to complete a nationwide rollout.

This isn’t the first time we’ve witnessed carrier PR departments trying to gain an edge with clever branding. In the late 2000s, there were numerous wireless technologies coming on the scene that offered performance improvements over 3G mobile data. One of them was LTE, and it was pushed by AT&T and Verizon. But Sprint was offering a technology known as WiMax, and T-Mobile’s technology was called HSPA+.

All of them were ultimately sold to the market as “4G,” creating a great deal of confusion over what “4G” really meant.

In 2010, Gizmodo tried to get to the bottom of it, concluding that all the carriers were engaged in a big marketing exercise. The market for 4G ultimately coalesced around LTE as a technology. But it wasn’t until 2012 that T-Mobile announced plans for its own LTE network.

Now, history stands to repeat itself as carriers jockey for advantage at the dawn of the 5G era. Different technologies branded as 5G, or even as the foundation for 5G, could still yield very different experiences, warns Harold Feld, a senior vice president at the consumer group Public Knowledge.

“Consumers in 2019 looking for a ‘5G’ experience need to be very careful and ask a lot of questions from vendors about what they are actually promising, and what are the limitations,” Feld said.