AT&T has announced plans to purchase more wireless spectrum. They will do so by acquiring the U.S. retail wireless operations of a carrier called Atlantic Tele-Network or ATNI, which is operated under the Alltel brand.

The deal, which still must get regulatory approval, will cost the second largest carrier in the U.S. $780 million in cash. Under terms of the agreement, AT&T will acquire wireless properties, including licenses, network assets, retail stores, and approximately 585,000 subscribers.

The acquisition includes spectrum in the 700 MHz, 850 MHz, and 1900 MHz bands and is said to be largely complementary to AT&T’s existing network. Under the Alltel brand, ATNI offers service to approximately 4.6 million people across six states. These include Georgia, Idaho, Illinois, North Carolina, Ohio, and South Carolina.

Once available in 34 states, most of Alltel was sold to Verizon Wireless in 2008. One year later, AT&T purchased additional parts of the company. In 2010, ATNI acquired the remaining 26 divested Alltel markets, including licenses, network assets and subscribers.

AT&T will announce the company’s quarterly earnings on Thursday, Jan. 24.