SMS EXTRADATA to 121 from your Airtel postpaid mobile to get the best offer on your Airtel mobile connection.
I got 1.5 GB 3G/4G data at Rs. 100 per month for my Airtel postpaid connection.
The MRP for extra 3G data on Airtel is Rs. 300 for 1GB and Rs. 500 for 2GB
Received sms for this offer. May be account specific. Try your luck.