The company will sell 26 million smartphones such as Apple Inc.’s iPhone and Nokia Oyj’s Lumia, up from a prior forecast of 25 million, said Ralph de la Vega, chief executive officer of AT&T’s wireless unit. AT&T had sold 6.4 million smartphones through November, he said today at a UBS AG conference.

While higher smartphone sales encourage more customer spending on data over the life of a wireless contract, they hurt profits at first because they’re often sold at a heavy discount. Susan Johnson, AT&T’s head of investor relations, declined in an interview today to provide a forecast for profit margins.

About one-quarter of users on Dallas-based AT&T’s shared- data service are choosing its 10-gigabyte plan, de la Vega said. That’s the third-most expensive shared-data offer at $120 a month, according to the company’s website. The service allows customers to combine as many as 10 devices under one monthly data alignment.

AT&T was little changed at $33.91 at the close in New York. The shares have risen 12 percent this year.