AT&T’s competitors have taken note of the company’s “5G Evolution” branding on phones and networks using 4G LTE Advanced Technology, but it hasn’t gone beyond crafty tweets or company blog posts–until now.

Sprint recently filed a lawsuit in federal court, seeking an injunction to stop AT&T from using 5GE tags on its devices or advertising.

In Sprint’s legal complaint, the company said it surveyed customers and found 54 percent of them believed AT&T’s “5GE” is as fast as, or faster than, actual 5G. Sprint also found that 43 percent of customers believed if they bought an AT&T phone today it would be 5G capable. According to Sprint, neither of those are true.

Basically, Sprint says AT&T is cheating. While AT&T did launch the nation’s first 5G network last year, it’s not available everywhere.

What AT&T calls 5GE is technology apart of the years-old 4G LTE-Advanced standard used by Verizon, T-Mobile, and Sprint on their 4G Networks. Despite this, AT&T has already incorporated 5GE indicators on some consumer’s screens.

“By making the false claim that it is offering 5G wireless network where it offers only a 4G LTE Advanced network, AT&T is attempting to secure an unfair advantage in the saturated wireless market,” Sprint wrote in a complaint filed in the US District Court for the Southern District of New York.

Sprint went on to claim “AT&T’s false and misleading statements deceive customers” and the company “seeks to induce consumers to purchase or renew AT&T’s services when they might otherwise have purchased Sprint’s services.”

In response to the lawsuit, AT&T said in a statement, “We will fight this lawsuit while continuing to deploy 5G Evolution in addition to standards-based mobile 5G. Customers want and deserve to know when they are getting better speeds.”

Public criticism is one thing, but an actual lawsuit with teeth may be too much for AT&T this time around. This isn’t the first time a new network has popped up, and it probably won’t be the last. Sprint’s actions could set a precedent for how the industry handles new networks, and how they’re marketed, for years to come.