NTT DoCoMo Inc. on Friday reported its first-ever fall in first-half earnings and revenue since it went public in 1998 due to a discount campaign to prevent its customers from defecting to rivals.

Citing the greater-than-expected number of users who opted for discount programs, the firm cut 100 billion yen from its initial full-year revenue projection but said it expects profit growth via cost cutting.

For the April-September period, Japan's largest mobile operator's net profit fell 6 percent to 335.19 billion yen. Revenue fell 3 percent to 2.45 trillion yen.