I Purchased a dual sim (CDMA & GSM) from karbonn mobiles last month. Iam using Tata cdma connection.from the day 1 I found that my voice to other call is not clear.i given it to service center and they return back me after 4 days saying that problem is resolved .later the problem found that it was not resolved.late when i approched them they said i getting new software which can resolve the issue but still not resolved,on my repeated calls they are not resolved can u suggest me how return it back.
please let me know wjere to compliant against this issue

mobile name:karbonn kc 441
network:tata indicom
cost of mobile:4900
warrarty- 1yr