A trick to get 500 mb of 3G in airtel for 7 days in free.
Many of you may b known to it.
You have to goto this link : http://3gdongle.airtel.in/
now on this page just click on ADD ALTERNATE CONTACT DETAILS .
Now add ur any email id and phone number,u will get i OTP (one time password)
on our thus new number which you will have to enter on that page and then just click submit.
And you will get 500mb 3G for free.
Note:— please open this link only with connecting internet with Airtel sim .
Contact me if any one faces any problem.