NEW YORK, Aug. 26 -- AT&T has agreed to buy the telecommunications company Netstream, based in Brazil. AT&T plans to initially invest $300 million in Netstream, which provides high-speed voice, data, video and Internet services to the corporate world. AT&T reports that it will continue to expand Netstream's roster of business customers in Brazil. Netstream began operations in October 1998, and today has more than 400 customers. The company is owned by Promon Tecnologia S.A., a Brazilian engineering, design and construction management firm. AT&T said that Netstream will continue to be managed by its current local leadership following its sale to the US telecom.