Oi. 

Oi S.A., a switched fixed-line telephony services concessionaire, provides telecommunication services in Brazil. The company offers fixed telephony services, including voice, data communication, and pay TV services; local and intraregional long-distance carrier services; domestic and international long-distance services; mobile telecommunications and corporate solutions; and maintenance, and repair services. It also provides call center and telemarketing, Internet, network, and Wi-Fi Internet services; and financial, and payment and credit system services. In addition, the company engages in the investment management activities, as well as raising funds in the international market. It serves residential, subscription and prepaid, mobile broadband, small, medium-sized, and large corporate customers. The company was formerly known as Brasil Telecom S.A. and changed its name to Oi S.A. in February 2012. Oi S.A. was founded in 1998 and is headquartered in Rio de Janeiro, Brazil. On June 20, 2016, Oi S.A. along with its subsidiaries filed for bankruptcy protection.