There is two way to get this offer first use the Official Facebook app. Download Facebook mobile app from https://www.facebook.com/mobile?_rdr and install it in your mobile, start Browsing Facebook without any Data charges.
If your Device is not capable of running Facebook Official mobile app then you have to send the message. Create new Message and Text “FACEBOOK” in capital and send it to 54321. Then you will receive reply from airtel Enjoy Free Facebook Browsing on Facebook Mobile Application till 6th Fab,2013. After that you can use facebook free from Facebook app Facebook for Everyone and from browser.
Note : Free Facebook Experience up to 500MB/Month.Valid on only Browsing on WWW.Facebook.com ,m.facebook.com and usage with Facebook mobile application. If you open any External link (out of Facebook) link will be charged as per normal rates and offer is valid till 6th Feb,2013.