AT&T recently started a shady marketing tactic that labeled its 4G network as a 5G network. Now, rivals Verizon and T-Mobile are not having any of it.

In an open letter, in which AT&T is not named directly, Verizon says in part “the potential to over-hype and under-deliver on the 5G promise is a temptation that the wireless industry must resist.” TechCrunch agrees. The advantages of 5G networks are profound. The next generation of wireless networks will bring more than just increased speeds, and AT&T’s current campaign of calling a 4G network a 5G network clouds the water.

T-Mobile is more direct in its criticism of AT&T. Because that’s how T-Mobile rolls. Watch.

didn’t realize it was this easy, brb updating pic.twitter.com/dCmnd6lspH — T-Mobile (@TMobile) January 7, 2019

This isn’t the first time AT&T has employed this mislabeling campaign. The wireless carrier did something similar prior to launching its LTE network; it was shady then and it’s shady now.

Disclosure: TechCrunch is a Verizon Media company.