Cox Communications (CCI) plans to rock the wireless phone business Monday by unveiling plans to launch cellphone service in the second half of 2009 that ultimately will make the No. 3 cable operator a rival of AT&T, (T) Sprint Nextel (S) and Verizon. (VZ) "We've spent $500 million buying wireless capacity in our markets," President Pat Esser says. "Now, we're going to turn it on." It's the most ambitious effort yet by a cable operator to bundle wireless phones with TV, Internet and land-line phone services. Operators have long seen cellphones as an important weapon to compete with AT&T and Verizon, which are rolling out TV services that compete with cable's core video business. Cable operators' efforts to forge alliances with Sprint stumbled over disagreements about marketing and service plans. Cox is betting that it can lure consumers with one-stop shopping and a lot of hand-holding for a cellphone service that neatly meshes with its other products.