This trick works for all Airtel numbers and call can only be made to airtel number only. Now dial these codes accordingly
* 337 #
You will see something like this after dialing those codes: Dear customer, you still have 100
HOW TO USE THE FREE CREDIT TO CALL?
Dial * 3 3 7 * 2 * airtel phone number# to use your free minutes. Enjoy and don’t forget to share on your timeline for others to get it.