The carrier activated 4.7 million iPhones during in the last fiscal quarter, but faced supply constraints of the device.
“We faced significant supply constraints in the third quarter, which clearly affected net (customer additions),” mobility chief Ralph de la Vega said on a conference call with analysts.
Overall, the company sold 6.1 million smartphones in the quarter, with Apple’s iPhone accounting for more than 77 % of its smartphones.
As for AT&T’s rival, Verizon Wireless announced last week that sold 651,000 iPhone 5 units in the third quarter.
In addition, AT&T added just 151,000 new postpaid customers, while Verizon added 1.53 million postpaid subscribers during the third quarter.
AT&T reported earnings of $3.6 billion for the third quarter, even with a year ago, nearly unchanged from the $3.62 billion from a year earlier.