Via Wikipedia:

Oi, formerly known as Telemar, but still legally called Telemar Norte Leste S.A., is the largest landline telephone company in Brazil, considering both lines in service and revenues. It is headquartered in Rio de Janeiro. Oi, along with Telemar Internet Ltda. (Oi Internet) and Companhia AIX Participacoes S.A., are subsidiaries of Tele Norte Leste [...]