For this you need android phone:
1.Recharge with a Data pack  example-103
2.Open your android mobile Default Browser .
3.In the address bar type live.airtelworld.com
4.Dont close the page till 510 seconds.
5.Now your net will be disconnected and you will se a ussd massage with 0.00 mb deducted from your main account balance.
6.Now open any web browser application or any application and use net.
7. Note Before disconnecting your internet
run the steps 2,3,4,5 again.
8.Now Check Your data balance. It will not deduct.