Karbonn — Not receive my mobile from service center from more that 2 month (under warranty)

Address:

Dehradun, Uttarakhand

I had purchase karbonn A21 on 27/12/2012 (In Dehradun), after 3, 4 month its starts problem in speaker and restart problem, finally i submitted my mobile in service center on 14/08/2013, They asked me to return back within 20 to 25days,
but till yet i didnt recieved my mobile, i visited many times in service center, they always misguide me on that.
For that i had contact to karbonn customer care, write mail on karbonn mobile care.but no positive response from karbonn side.now i dont know what to do
mobile - karbonn A21
imei-[protected]
service center-Ujjwal telecom, Dehradun
job sheet no.-KJASPUT024813K3476
my mobile no.- [protected]