Compare to "Uninor [India] Shifts "from data to Internet"; Charges for Facebook and Whatsapp Use" - here, "Vodafone India Offers Free Twitter Access" - here and "Facebook Offers Free Messaging Through 18 MNOs" - here.
Back to Aircel - "Under the offer, Aircel will provide free 50 MB per month data on Facebook for a period of 60 days after activation. Existing customers will get free 50 MB data for 30 days and post 50 MB usage, the subscribers will have the option of using Facebook on their phones at ₹0.02 per 10 KB .. The customers also have the option of benefiting from the special tariff packs for Facebook which will be as low as ₹0.50 per day".
See "Aircel offers free Facebook access to its customers" - here.