AT&T says it will buy T-Mobile USA from Deutsche Telekom in a cash-and-stock deal valued at $39 billion. The deal will combine the second-largest wireless carrier in the US with the fourth, notes the Wall Street Journal, which adds that it comes on the heels of AT&T's loss of its exclusive hold on the iPhone. The companies said that by combining, some spectrum shortage issues would be alleviated. The Journal reports that it's not yet clear whether or not regulators would OK a move that would reduce the number of US wireless carriers from four to three. The new entity would have about a third more subscribers than Verizon, and twice as many as Sprint.