 to lower the cost of selling services to small businesses. Today many agents sell telephone services as an adjunct to the telephone and networking systems that they offer. Agents are certified and receive some training from the telephone companies they represent. They do not bill customers directly for Competition, Industry Structures, and Regulations the voice and data services they sell; rather, customers receive bills directly from the carriers. Primarily small and midsize organizations use agents because they are often easier to reach and some have the ability to help troubleshoot problems when it is not appar- ent whether the problem is in the carrier's connections or the onsite equipment. Smaller competitive carriers also use agents. Moreover, carriers often prefer to serve smaller business customers with agents to reduce their own staffing and selling expenses. Retail outlets such as Best Buy, Radio Shack, and Staples act as agents for cellular providers and prepaid cellular services. Wal-Mart and Amazon sell acFone's prepaid mobile phones and services. In addition to large retailers, there are often networks of small retailers that act as agents for larger companies such as T-Mobile and Verizon Wireless. The small retailers display the logos of the carriers that they represent in their stores and sell hardware and accessories for mobile phones in addition to service plans. Resellers Like agents, resellers do not own network infrastructure. Unlike agents, however, resellers provide billing and customer service for their customers and market services under their own brand. Resellers sell wireline service such as data (T1, T3, and other high-speed services), calling cards, Internet access, local calling, long-distance, mobile services, VoIP services, and international calling. Resellers purchase services at discounts, mark them up, and often offer them at below retail cost. Resellers offer services carried on networks owned by AT&T, Sprint, Level 3, Verizon, and other carriers, worldwide. Competitive provid