Update: AirTel has recently discontinued the SMS activation and deactivation service for GPRS/Mobile Office. You now need to call 56561, press 1 for English, press 1 to activate GPRS. It takes about 2 to 4 days to have GPRS activated, painfully slow. To deactivate GPRS or Mobile Office, call 56562, press 1 for English, press 1 to deactivate GPRS.
To activate, SMS “GPRSACT” to 511. AirTel will begin charging you Re 14.99/- per day. You will need to SMS “MO” (Mobile office?) to 501 for the precise settings for your phone (I did not get a response with settings as promised), or call their customer-service.
To deactivate, send “GPRSDEACT” to 511.
AirTel LIVE! and GPRS are not the same. For AirTel LIVE, I suggest you start with the AirTel web portal and FAQ on AirTel LIVE by clicking here.