eBay India — The company is not following their guarantee procedure

I bought a phone Micromax Canvas A1 from Ebay India dated 11 March 2015.As per the Micromax gurantee they replace the phone in 7 days.But the phone works fine in first 7 days after 7 days phone battery backup is too worst.As per Ebay guarantee they replace the phone in 30 days after buying any product as itis not upto the description shown on their page.At their page phone's battery backup is 6 hours while using 2G internet but it is only 30 minutes on using internet.SO I need replacement.So I contact them for replacement but they just making fun of me & answered me that Ebay is shop & we are not responsible for that.The manufacturer responsible for that.As per in my case Ebay India is East India Company.