Asus India — Asus zenfone 2 ze550ml

Address: Gurgaon, Haryana, 122002

Website: www.flipkart.com/support

I bought a asus zenfone 2 ze550ml from flipkart on july 2015. Its having several issues from day 1 when i purchased it, sim slot was not supporting, then i replaced it with new one.
Now again its automatically switched off and is not switching on,
i showed it to service center on april 2016 they denied it to take under warranty because motherboard has a small spot which they were saying that its a water mark. They showed it to me. And said its moisture which will not cover any warranty. But it couldn't be a watermark it is like soldering machine spot. And motherboard costing was 12536 while i purchased the phone worth 12995, it means you are looting people.
After 2---3 days phone automatically switching on and off. And is taking more than 12-15 hours to charge,
now i just want to ask you if there is problem in motherboard how is it working again. And how there is moisture in motherboard while phone never dropped in water.
I am looking for your favourable response