Aiming to lure away rivals' subscribers while retaining their own, NTT Docomo Inc. on Thursday unveiled new monthly subscription plans that include a fixed rate for unlimited domestic calls and its first data sharing plan for smartphone users.

The plans take effect in June.

Docomo said its basic ¥2,700 monthly fee will include unlimited calling for smartphone users, which is good news for people who make lots of calls. Docomo customers currently pay ¥20 for every 30 seconds on top of the basic service, which costs ¥743 a month.