Here’s a sign of just how much burning hatred T-Mobile and ATT have for one another: They’re willing to engage in a public social media fight over one single customer. The Next Web notes that ATT customer Jay Rooney took to Twitter this week to voice his frustrations with ATT and asked the carrier why he shouldn’t switch to T-Mobile to take advantage of its free international data roaming plan. ATT warned Rooney that switching to T-Mobile would be “scary” and took a shot at the carrier’s much-maligned wireless network. T-Mobile hit back and asked ATT whether its “kindergarten panel” wrote its jokes. In the end, Rooney said that he’d visit a T-Mobile store and would ask about switching to