Trick will work only in regions where sms10 plan is available.
the trick is very much simple
activate sms10 in morning after 10am by sending sms10 to 51619 your 1 rs is not cut now send all sms at 10ps
now at night deactivate it before 9pm by sending dsms10 to 51619.it will deactivate
next day do again the same way
note if you dont deactivate it at night you will be charged rs.1

Try At ur own risk.. i im not use this trick bcz i hnt airtel no.. my frnd give me this trick...
hello frnds plz give me idea free gprs trick .. thx jhankaarbeat.com for give me free 50 rs recharge...