Oi SA, formerly Brasil Telecom SA, is a Brazil-based holding company engaged in the telecommunication sector. The Company is primarily involved in the provision of fixed telephony services in Brazilian states of Acre, Rondonia, Mato Grosso, Mato Grosso do Sul, Tocantins, Goias, Parana, Santa Catarina and Rio Grande do Sul. Additionally, it offers a range of integrated telecommunication services, including mobile telecommunication services, data transmission and Internet service provider (ISP) services, among others. The Company provides services to residential and corporate customers. Through its subsidiaries, the Company is also involved in the operation of call centers, including telemarketing and customer services, and in the provision of payment cards. As of December 31, 2011, the Company had a number of subsidiaries, including 14 Brasil Telecom Celular SA, Brasil Telecom Comunicacao Multimidia Ltda, BrT Card Servicos Financeiros Ltda and Vant Telecomunicacoes Ltda, among others.