Asus India — Zenfone 5 battery issue

Address: Mumbai City, Maharashtra, 411057

I have taken phone 9/11/2014. Model (A501CG) and there now from past 1-2 months battery is draining quickly.
Time to charge battery is 3 hrs and time to discharge when I am using it over wifi then 3-6 hrs maximum. Also if I am not using my phn then too battery is draining drastically. Suppose I am sleeping by 11-12 pm with 80% charge on my phn then when I wake up in morning around 8-9 am, battery is full discharged and switched off.

Please suggest me what could be the possible reason for this.
Also provide me working customer care center details in Pune(Near Hinjewadi) and Mumbai(Near Malad)

Mobile - [protected]
Email - [protected]@gmail.com