Alltel and U.S. Cellular announced a new partnership on Monday in which the two carriers will offer a new U Prepaid service directly from Walmart stores. The service will launch in May in 500 Walmart stores across the United States. The carriers said U Prepaid will offer “simplified, easy-to-understand service plan choices,” although it’s unclear how much those service plans will cost. U Prepaid wil launch with four devices at first, including the Samsung Repp, the LG Attune/Exchange, the LG Saber and the Samsung Chrono. Text and data plans will be available and customers will be able to roam across both Alltel and U.S. Cellular networks. U Prepaid will certainly see stiff competition from Apple’s new in-store iPhone displays, however.