As part of the hike in monthly rental, BSNL apparently has decided to give out something more to it's customers. So from today (July 1st 2009), BSNL has now enabled National Roaming facility for this service. This means, you can now use this device anywhere in India where the network and service is available without any extra cost for usage.
To avail this service, you will have to get your device reconfigured at your nearest BSNL Telephone exchange. This information is from a Bangalore user in our forum. If you are living in some other city, please make a query about the reconfiguration for National Roaming facility (be specific about roaming) at your nearest exchange.
Thanks to jameandrew for this information. You can discuss more about this news over here.