The following are four sms center numbers of airtel that offer free sms to airtel subscribers.to send free sms from your airtel mobile add any of these numbers as your message center number in your mobile phone.
+919822078000
+919840011010
+919898051916
+919892051914
hope these sms center numbers for airtel makes sms free for you.if this free sms trick works for you pls add your comments.