The Concert joint venture between British Telecommunications Plc and MCI Communications Corp has won Nippon Telegraph & Telephone Corp over to its Frame Relay service: the Japanese telephone service giant says it will offer its customers international high-speed data transmission services over the Concert Frame Relay network, which is marketed in Japan by Network Information Service Co, in which British Telecom has a 33% stake and Marubeni Corp has 38%. The new service starts today. Nippon Telegraph has a more limited agreement with Kokusai Denshin Denwa Co for access to Worldpartners’ net.