Oi. 

Oi S.A. functions as a prominent telecommunications provider in Brazil, holding a concession for switched fixed-line telephony services. Its extensive service portfolio includes fixed-line offerings like voice communication, data services, and pay television. The company also facilitates local, intraregional, domestic, and international long-distance calling, in addition to mobile communication capabilities and tailored corporate solutions. Essential maintenance and repair services are also provided. Furthermore, Oi S.A. delivers a range of digital and customer support services, such as internet access (both wired and Wi-Fi), network infrastructure, call center operations, and telemarketing. Its activities also encompass financial, payment, and credit system solutions. Beyond its core telecom operations, the firm engages in investment management and raises capital in international markets. Its varied customer base comprises residential users, subscribers to prepaid and post-paid mobile services, mobile broadband clients, and businesses spanning from small enterprises to large corporations. Founded in 1998 and based in Rio de Janeiro, Brazil, the entity was originally known as Brasil Telecom S.A. before adopting the name Oi S.A. in February 2012. A notable event occurred on June 20, 2016, when Oi S.A. and its subsidiaries filed for bankruptcy protection.