AT&T said on Friday it will acquire prepaid wireless provider Leap Wireless in a deal valued at about $4 billion, including debt as large carriers scramble to accumulate valuable spectrum. Under the agreement, AT&T will acquire all of Leap’s stock and approximately 5 million subscribers for $15 per share in cash or about $1.2 billion. The offer represents a premium of 88 percent to Leap’s Friday closing price of $7.98. As of April 15, Leap had $2.8 billion in debt, the companies said in a statement. Leap’s shares more than doubled to $16.80 in after hour trade after closing at $7.98 on Friday. The deal is the latest in a series of acquisitions in the wireless industry and follows Softbank’s acquisition of Sprint. As the No. 2 wireless provider in the United States, AT&T has been looking to grow in a mature market and has been urgently seeking access to additional wireless spectrum.