Lenovo Mobile — I am complaining about my new lenovo k4 note

Address:

Ahmedabad, Gujarat, 380015

Hello,
I purchased lenovo K4 note vibe in the month of January 2016, after one months problems get started like not updated software and all so I submitted to authorised service centre and they did, after fews days again some problems in voice hearing, hang, display problem, battery problem, and many others, so I submitted again to authorised service centre and they changed mother board of particular mobile and gave to me but again problem didn't solve so at a same time I again submitted and they changed mother board again and gave it to me after fews days and I updated some applications and on the same days I am facing some other problems likes calls drops automatically while I Dail so I again submitted on 13 may 2016 and coordinate with Mr Ramashankar who is West region heads and confirmed me that we will replace it soon once I get approval but after our that conversation it's almost 13-15 days gone but till date I am not getting any revert and I visited ahmedabad authorised service centre and they also told me.that we didn't receive any confirmation. Once we get it we will replace and in his system also mark that we have to replace this mobile but I am not getting any proper revert from lenovo service department and I am fed up with this kind of issues. I purchased this mobile before 5 months but hardly I used 2 months and 3 months in service centre so what should I do in this case if someone body help me.