Free Airtel Latest Offer-100 mb for 1 Week for Free

Recently my friend told that he got some trick regarding airtel. I eagerly asked what is that and he revealed the trick. This is not a trick,I think but most of us couldn't know the offer. Just dial
121314 and press 1 twice. Either you will get 100 mb for free or you get a saying"Insufficient balance" . Try your luck and enjoyy. Comment if it's working or not.