Airtel has introduced  'Call-me-Back ' service to allow a prepaid user to get a call-back from another Airtel number (prepaid or postpaid) in case of insufficient balance. This unique service will ensure that airtel customers are always connected.
 
Just SMS writing CALL <space> <airtel mobile number you want to speak to .>, send to 121 , and expect a call from your dear ones. For e.g. 'Person A' having balance less than Re.1 can send a toll-free SMS to 121 writing CALL < Person B airtel number >, and the 'Person B' will get an SMS from number of 'Person A' saying : "Please call me back. Thank You." .This service will ensure that are airtel customers are never out of touch with their family and friends.
 
There is no charge to 'Person A' for this service, and the call-back by 'Person B' is as per the person's B plan rate. The customer who is calling back can be a prepaid or a postpaid user. Also, both the customers can be a local , STD number , or be in national roaming.
 
This service can be availed when the balance in customer's prepaid account is below Re1, and can be used up to 3 times in a day.