Update:
I had complained regarding the extra IDV charge to Airtel DTH. Just received a call from the customer care, they informed the following:
1. Any addition to the UDP plan will add extra IDV charge of ₹26
2. This is also applicable to the existing users.
Since I had taken UDP package 3months back and there was no IDV charge then, so customer care credited my account with ₹234 which will be adjusted against the IDV charges for the remaining 9 months.
So, existing customers who are facing the same issue, kindly contact customer care.