Finally after mailing everyone and got no response had to raise a complaint with the M.I.B. Sent a copy of the complaint to Airtel and soon an engineer visited my place and agreed to replace my STB free of cost.
The STB was replaced today but the STB which was replaced shows Signal level around 75 and signal Quality fluctuates btwn 00 and 05, I get clear audio video on these channels (ch 100,101 and few others.) Checked the quality on other channels the signal level is above 85. I once again asked for replacement as I am not getting proper signal. Now I think I have the Huwaei brand STB. Is this normal to get this quality in this STB? Cause my previous Kaonmedia STB had signal quality of above 90 on all channels.