Follow the Simple steps given below,
1.Dial
543211888 (toll free)
First Activate Caller Tune for one month.
2.Now,Dial
5787881 Here you just activate a New Song for 3 Months.
3.Thats it! Everything done! You can Enjoy Free Caller Tune on Airtel.
I hope you'll Try it and do post your comments below,so that it may help other friends too..