Consumer Redressal

I have bought my mobile on 29/9/2014. after that my mobile i not working properly so i have submitted mobile to aaradhya service centre. they have replaced each an every part of my mobile but the also it was not working, after that they change motherboard 2 time but no solution. then they gave me replacement of mobile two time but still same problem.now i have requested for cash back but they are not ready for that nor they are replying to my mails.they are like ignoring me. its already two and half months, my mobile is in sony service centre.