KDDI Corp , Japan's No.2 mobile phone operator, said on Thursday 1,200 of its users switched to rivals in July using number portability, logging a loss for the first time since the option was introduced in 2006.

Number portability means customers can keep their number when they change mobile phone operators.

Rivals Softbank Corp, which introduced Apple Inc's iPhone in July, and NTT DoCoMo Inc will announce their subscriber figures later in the day.

With new sign-ups, KDDI added 17,000 net users in July.

Source:Reuters