Oi. 

Oi S.A. operates as a prominent telecommunications provider in Brazil, holding a concession for fixed-line telephony services throughout the nation. The company delivers a wide spectrum of services, including traditional landline telephone services like voice communication, data transmission, and pay-TV subscriptions. It also acts as a carrier for local, intra-regional, domestic, and international long-distance calls. Further expanding its portfolio, Oi S.A. offers mobile telecommunication solutions, bespoke corporate packages, and critical maintenance and repair services. The company's diverse offerings also extend to call center and telemarketing operations, internet access (including Wi-Fi), network infrastructure, and a variety of financial, payment, and credit system services. Additionally, Oi S.A. engages in investment management and secures funding from global markets. Its clientele spans a broad range, from individual residential customers and mobile broadband users (both prepaid and postpaid) to small, medium, and large corporate enterprises. Established in 1998 as Brasil Telecom S.A., the firm officially adopted the name Oi S.A. in February 2012 and is headquartered in Rio de Janeiro, Brazil. A notable event in the company's history was its filing for bankruptcy protection, alongside its subsidiaries, on June 20, 2016.