In a three-pronged deal valued at about $3.3 billion, AT&T Wireless purchased networks in San Francisco, San Diego and Houston. The company will sell wireless service under its own name in the nation’s 15 largest markets-the three cities were the last in which AT&T lacked branded service.

The acquisitions will add 1.3 million customers and represent about $850 million in revenues, not including roaming charges, and more than $300 million in operating cash flow. AT&T promised an aggressive campaign to add customers in the three markets, whose combined population is 15 million. AT&T has more than 10.1 million wireless customers.