If your Airtel sim card is having enough data but it's validity is about to expire.. Then with this trick you can Increase validity of Airtel data pack & even for Unlimited days. But it will cost you 1rs/Day . ★ Steps → 1) First Dial This USSD Code *129# in your Phone Dialer. 2) After Dialing above USSD Code, now It will open night store, Now you will see a option of Unlimited facebook pack for 1 day. 3) Now Activate this Unlimited facebook pack for 1 day.. 4) Done !! It will Increase your Data pack validity for 1 Day in 1 Rs . 5) Repeat this Process Daily to extend the validity in Just 1 Rs.