Airtel - Additional for recharge through Airtel thanks app was not activated

I have done an add on pack of Rs.** on ** July **** through Airtel thanks app and I also received coupon of additional * gb. I redeemed the *gb coupon and it was not activated and also the coupon was not available anymore. I only received the normal *gb of which *gb was used to repay my *gb data loan. I tried to raise a complaint through Airtel thanks app and also through email and the reply for mail is that they will resolve the issue within ** hours and now it is more than * days and still my issue is unresolved.