Many of my friends in India use BSNL DataOne Broad Band connection because it's quite cheap on pocket, but many of them have problem viewing there data usage status.
Here is the link to check it :
Just navigate to the following link and enter your username and password provided to you. You will be displayed few menu options. Click on "Service Records" and check the data usage of the required month.
Note : Use Internet Explorer as the browser and if the link above does not work, then reset all the settings of IE and clear all cookies and history and restart the browser.