Seoul: More than 50,000 customers of KT Corp., South Korea's second-largest mobile carrier, have canceled their subscriptions after the telecom company began waiving early termination penalties following a major data breach, industry sources said Friday. According to Yonhap News Agency, 52,661 KT users moved to rival carriers between Wednesday and Saturday. More than 70 percent of them switched to SK Telecom Co. On Saturday alone, 21,027 people left KT, including 13,616 who opted for SK Telecom, the sources said. SK Telecom, the No. 1 mobile carrier, has been moving swiftly to attract KT customers, including those who previously left the company following its own hacking incident last year, prompting some former users to return.