Micromax — Service Delay not returning my mobile.

I purchased a micromax mobile A350 in October 2014. 3 months back mobile battery got buldge.it was under warrant and hence I have given mobile to there service center "mobile seva" marathalli, bangalore on 11/04/2015 and from that time onwards till date made many call to micromax customer care . every time they say it will take 2 weeks more.. Neither service center nor micromax are giving the mobile back and when I ask for refund they are saying they can''t do it as it is out of policy. I am suffering from this mental torture from last approximately 3 months. Please take this matter and help me out of this micromax mess Thanks, Dheeraj