Why cant I get SMS updates?? Help needed!!

I don't seem to be getting updates via SMS. My device is added, verified and the device notification is turned on. I'm in India and use Vodafone. I use the 5566511 shortcode. When I send commands like ON to the shortcode, I get a confirmation from Twitter. Almost immediately, I get a SMS from 55665 saying "The service is not enabled yet". Any help will be greatly appreciated.