Flipkart — return or replacement of p99 panasonic mobile set

I have purchased a P99 set through online. After receiving the set and during its usage, I noticed that the discharging rate of the battery is very high. Immediately, I brought the matter into the knowledge of the authority through online. Unfortunately, the authority arose several queries about the problem, but my problem has not been solved yet. I also agreed to replace the set with another set, but all my attempts went in vain. I also like to mention that I used to purchase many items from the company like Flipcart and sometimes I returned few items, but I never faced such problem before this which goes against the reputation of the organization. So, I would request your kind favour to look into the matter to work out my purpose.