Asus India — My mobile is frequently getting heat even in cold place also

Address: Krishna, Andhra Pradesh, 520007

Website: asus

My mobile phone frequently getting very heat.
I 'm buy "asus selfie zenfone" on flipkart. The flipkart deliverd on 31/05/17.
While unboxing my mobile first time i switched on and do some strating operations like gmail setting and etc..
After 5 minutes my phone getting warm i feel very bad.
And after one day when i on the mobile then it getting in warm i don't install any application and i also unstall some default apps but my phone is getting very heat.
Especially the back side of near volume buttons getting very heat even in taking camera also.
I tested in ac room also but i don't feel any better.
*plz give me reply or tell me whether i received product is damaged*