Apple's iPhone 6 Plus selling unexpectedly well as supply equalizes, says T-Mobile CEO

In an interview at the Code/Mobile conference, Legere told Re/code's Ina Fried that, while both iPhone 6 models are selling well, the iPhone 6 Plus outperformed T-Mobile's estimates. The carrier was expecting the smaller 4.7-inch iPhone 6 to account for about 75 to 80 percent of all new iPhone sales.

"Overall demand for us was huge," Legere said. "We got hammered by it."

Apple CEO Tim Cook also noted high demand for the 6 Plus during the company's fourth quarter conference call last week, saying supply may not catch up until 2015. Legere sees 6 Plus supply slowly making up ground on demand, but it's uncertain when customers will be able to simply walk in off the street and find one in stock.

Legere is acutely aware of the iPhone's importance to T-Mobile's success and getting the Apple handset on the carrier's network was one of his main goals when entering as CEO. T-Mobile today announced quarterly results, with a best-ever performance of 1.4 million post-paid net adds and service revenues at $5.7 billion, up 10.6 percent year-over-year.

"Get on your knees, crawl over there, do whatever the hell you have to do," Legere remembered saying to employees. "Your store without the iPhone in it is shit."

On the topic of Apple SIM, the T-Mobile chief again went over how the new micro-SIM card works. Apple introduced the multi-carrier micro-SIM with the latest Wi-Fi + Cellular iPad Air 2 and iPad mini 3, advertising that users are able to hop from carrier to carrier without swapping out cards. When the tablets went on sale, however, it was discovered that units connected to AT&T's network were being locked in, requiring customers get a replacement Apple SIM from Apple or their new carrier when switching.

Wireless companies participating in the Apple SIM program — AT&T, T-Mobile and Sprint in the U.S. — get iPads to sell with Apple SIMs already tied to their respective services, with AT&T permanently locking the card in to its network. Cellular iPads purchased from an Apple Store are not tethered to any one carrier out-of-the-box and may therefore be the better choice for consumers at this time.