Make the most of it, I personally tried and received free 10gb data every month for 3 months. 
"
Today is a day of celebrations.
Dear Customer,
We are celebrating your brand Airtel being declared India’s fastest mobile network. Coming from the world’s largest and most credible speed test organization, Ookla, this is no mean feat.
You know our celebrations would be incomplete without you. And we want to thank our valued postpaid customer, you, for being a part of our journey. Because words don't suffice, we would like to give you an Airtel Surprise.
We are sending some free data your way, so that you can enjoy India’s fastest mobile network a little more. Just SMS SURPRISE to 121 from your Airtel number.
We hope the years to come bring with them more milestones that we cross together and many more moments that help strengthen our bond.
I want to extend my warmest wishes to you and your family on the festive occasion of Holi. Go ahead, claim your Airtel Surprise and share the celebrations with your loved ones.
Best regards,
Gopal Vittal
CEO, Bharti Airtel Ltd."

"
Today is a day of celebrations.
Dear Customer,
We are celebrating your brand Airtel being declared India’s fastest mobile network. Coming from the world’s largest and most credible speed test organization, Ookla, this is no mean feat.
You know our celebrations would be incomplete without you. And we want to thank our valued postpaid customer, you, for being a part of our journey. Because words don't suffice, we would like to give you an Airtel Surprise.
We are sending some free data your way, so that you can enjoy India’s fastest mobile network a little more. Just SMS SURPRISE to 121 from your Airtel number.
We hope the years to come bring with them more milestones that we cross together and many more moments that help strengthen our bond.
I want to extend my warmest wishes to you and your family on the festive occasion of Holi. Go ahead, claim your Airtel Surprise and share the celebrations with your loved ones.
Best regards,
Gopal Vittal
CEO, Bharti Airtel Ltd."