Redmi Mi 1S — Liquid Damage

I purchased one Redmi Mi 1s through Flipcart. Since I got this phone some problems related to battery back up I noticed and after 3 month I communicated recognized Mi service center and they told me the problem arose because of software issue and they solved it. then after 10 or 15 days of this repair the same problem I faced and now when I went to service center, they are telling like my device shows liquid damage and also charging Rs 850 for it. But I told them if it had been there, then you people would have told me much time before, when I first came here with the issue. Finally no support from there end I got and also I tried to communicate the Mi customer service by dropping a complaint mail and repeated call, but no response till date also I get.