A Japan-based affiliate of British telecommunications giant Cable & Wireless PLC has asked the Fair Trade Commission to probe sales practices by Japan's dominant Nippon Telegraph and Telephone group over the Myline service for registering preferred carriers.

Officials of Cable and Wireless IDC Inc. said salespeople for NTT East Corp., NTT West Corp. and NTT Communications Corp. are telling telephone users they may have trouble getting telephone line repairs if they register with a non-NTT carrier.

Cable & Wireless IDC has already filed a similar complaint with the Public Management, Home Affairs, Posts and Telecommunications Ministry and with an industry organization.