John Legere, the brash new CEO of T-Mobile says the "uncarrier" is just getting started. 

When asked about the war of words with AT&T over the strength of the companies' networks, Legere said the major carriers are in for a surprise if they think he's bringing down the intensity of his rhetoric any time soon. 

“What can I say? It’s fun to see AT&T starting to sweat—while we’re just warming up," Legere told Wireless Week in emailed comments. "Look, the big phone companies have been rigging the game for too long. And they’ve held all the cards. They’re learning we aren’t playing their game. And that we’re giving consumers a fair deal.  So, if they don’t like what we’re doing now, just wait. It’s going to get better. This is fun. We all know how the story of David and Goliath ends.”

While some may say the nation's fourth-largest carrier is biting off more than it can chew, it really doesn't have much to lose. Until now, T-Mobile has been leaning heavily on the strength of its  high-speed HSPA+ network, which currently covers 225 million people. On the LTE side, however, T-Mobile is far behind its larger rivals. The company says it aims to cover 100 million people by the middle of 2013 and more than 200 million by the end of the year. The company reports finishing LTE upgrades in Las Vegas, NV and Kansas City, MO.

Meanwhile, AT&T and Verizon are promising that their LTE rollouts will be completed by the end of 2014 and 2013 respectively. 

T-Mobile and AT&T appear to be officially at each other's throats with their latest marketing antics. 

Last week AT&T lashed out at T-Mobile with full-page ads in the New York Times, Wall Street Journal and USA Today that appeared to be defending the honor of its network against attacks by Legere, who has publically called AT&T's network "crap." 

The ads from AT&T claimed that T-Mobile's network is only half as fast as AT&T's and drops twice as many calls. At the bottom of the page is text that warns, "Don't be fooled by their misleading claims. For the better network experience count on AT&T.”

Now it appears T-Mobile is responding directly to AT&T with new ads that ask the question, "If AT&T thought our network wasn't great, why did they try to buy it?"

Proofs of the ads were leaked Wednesday by, which said the ads may run as early as yesterday. The outlet said the ads were designed by the same agency that put together T-Mobile's most recent television spots.

T-Mobile's tough stance certainly shouldn't come as a surprise to AT&T. During remarks at parent company Deutsche Telekom's annual investor conference back in December, Legere was up front about how the carrier would proceed, as it awaits more spectrum through its proposed acquisition of MetroPCS. 

"You love your iPhone, but you hate AT&T. I want you to get used to that kind of tone, because that is the way we're going to play," Legere said.  

The heated rivalry between the two carriers comes after regulators thwarted a $40 billion acquisition of T-Mobile by AT&T, leaving both companies to pick up the pieces of what they thought should have been a done deal.