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At times, the heads of Sprint and T-Mobile are united by their competition against two larger rivals with way more market share and resources.

Then sometimes, Marcelo Claure and John Legere really just get on each other’s nerves.

“I am so tired of your Uncarrier bullshit when you are worse than the other two carriers together,” Claure said in a tweet to Legere Thursday, which took T-Mobile to task over its Jump On Demand program, which Claure called a “cheap misleading lease.” Claure said that T-Mobile makes much of the fact that customers can upgrade up to three times a year, but doesn’t highlight the fact that the monthly cost can go up when they do.

Claure’s tweet came in response to one from Legere which criticized Sprint’s latest plan, known as All-In.

https://twitter.com/marceloclaure/status/616456296758439936

The new promotion, as noted by Re/code, actually represents a higher price for iPhone customers than a prior offer and doesn’t necessarily make customers’ bills any clearer.

It’s not the first Twitter fight between the two, though at times they have also praised one another in their efforts to take on what both call the AT&T-Verizon duopoly.

Legere is known for picking fights on Twitter, having launched volleys against not only wireless rivals, but Donald Trump as well.