Airtel is now offering 20 GB free additional data for one year with its rupees 399 plan.The motive of Airtel on this additional data is to beat Vodafone 399 plan. Airtel and Vodafone are both notably providing unlimited local STD and roaming calls. Vodafone is also giving access to a one year Amazon Prime subscription with its 399 plan and Airtel also providing a wink music service with its plan of rupees 399. With the Airtel 399 postpaid plan you can get 20 GB of 3G or 4G data every month for a year. Also this plan includes unlimited local and STD calls along with free SMS of 100 per day for the entire billing cycle.