Atlanta-based AT&T Mobility turned on 4.7 million iPhones between July and September, but the devices mostly went into the hands of current customers.

The nation’s No. 2 wireless carrier said Wednesday that only 18 percent of those customers were new to the company.

A shortage of the latest iPhone version, which didn’t go on sale until the last week of the third quarter, was a key reason behind the lackluster addition of new customers. Pent-up demand with AT&T’s current iPhone customers made up the majority of the sales for iPhone 5.

Ralph de la Vega, chairman and chief executive officer of AT&T Mobility, said that’s no different than during any other time a new iPhone has gone on sale.

“Each time there is a new iPhone, we see strong and immediate demand for it,” de la Vega said.

He added, “There is typically a supply constraint, and it usually eases up.”

Overall, AT&T Mobility added only 151,000 of what’s called post-paid wireless customers, ones that sign long-term contracts. Those customers are deemed the most lucrative because they agree to stay with the company longer and typically buy more expensive wireless and data plans.

De la Vega said the demand for the new iPhone is likely to increase as the holiday season draws closer. There will be plenty of inventory, however, to allow the company to add new customers.

“I feel very comfortable that we’re in a position that we’re going to be able to add additional customers as supply becomes available,” he said.

Overall, AT&T sold 6.1 million smart phones during the quarter. The company reported record sales for Android and Windows smart phones.

Parent company AT&T, based in Dallas, posted a third-quarter profit of $3.64 billion, or 63 cents a share, compared with a net income of $3.62 billion, or 61 cents a share, during the same time a year ago. Revenue for the quarter, ending Sept. 30, was $31.46 billion, compared with $31.48 billion a year ago.