Mobile manufactural problem

Location/place: Azamgarh,up

Name of company/service: Karbonn mobiles

I bought my KARBONN K1616 mobile 6 month ago.In this time i send my mobile 3 times sevice center,but mobile does not working properly. I talk to incharge karbonn mobiles up for refunding or replacing my mobile but he did not help me
Please help me in replacing of my mobie