Steps to follow.(It will be available free if you have free national sms pack and if you are not a Aircel India and Tata indicom subscriber)

1.Should register your mobile phone in facebook.

2.To register with facebook. you have to go to acccount->account Settings

3.Then click on mobile tab.

4.Click on Register for Facebook Text Messages.

5.Choose Country and Mobile Carrier in step 1.Then click next

6.SMS F 9232232665

7.Confirmation code from facebook will be sent to you. Enter the confirmation code in step 2 and register your mobile in facebook.

8.To update status of simply type the message and send it to 9232232665.

9.To post on your friends wall type wall and send it to 9232232665.

for more details visit http://www.facebook.com/mobile/?texts