DOW JONES NEWSWIRES U.S. Cellular Corp. (USM) has teamed with Alltel Wireless to sell "U Prepaid" no-contract wireless service in nearly 500 Wal-Mart Stores Inc. (WMT) locations starting next month. Cellphone-service provider U.S. Cellular has been steadily losing postpaid subscribers amid fierce competition in a wireless industry nearly saturated with cellphones. Alltel Wireless is a unit of Atlantic Tele-Network Inc.'s (ATNI) Allied Wireless Communications Corp. The U Prepaid service will run on either U.S. Cellular's high-speed national network or Alltel's coast-to-coast network. Customers will be able to choose from multiple data options and plans that include unlimited talk and texting and can pick from four devices: the Android-powered Samsung Repp, the LG Attune/LG Exchange, LG Saber and the Samsung Chrono. "Teaming with Alltel to gain distribution in Walmart gives us another opportunity to be where our customers want to shop and to offer more customers a prepaid service that helps them control their monthly budgets," said Carter S. Elenz, U.S. Cellular's executive vice president of sales and customer service. Last month, Standard & Poor's Ratings Services lowered its ratings outlook for Telephone & Data Systems Inc. (TDS) and its U.S. Cellular unit to negative from stable, citing increased competitive pressure at the U.S. Cellular unit. -By Melodie Warner, Dow Jones Newswires; 212-416-2283; melodie.warner@dowjones.com