AT&T Mobility ( T ) looks to have hit an iPhone wall, with the iconic device still remaining a big seller for the carrier, but a greater share of new customers looking elsewhere when selecting the device. AT&T Mobility said it sold 5.5 million smartphones during the first quarter, representing 78% of all postpaid device sales. Apple's iPhone models accounted for 4.3 million of those smartphone sales. Macquarie Equities Research noted smartphone sales came in below estimates, which was attributed to share losses versus Verizon Wireless. The firm said it expected this trend to accelerate in the run-up to a potential LTE-equipped iPhone launch later this year. Macquarie Equities noted that Verizon Wireless's dominance in postpaid growth has been strong since the first quarter of last year and that it has also bested AT&T Mobility in iPhone sales since beginning to offer the device just over a year ago.