BSNL didn’t provide me a proper link to check my usage. However one of my friends gave me a useful link where we can check and track the amount of data uploaded/downloaded on everyday basis. All BSNL users can make a note of this link to check usage:
Login with the username and password provided by BSNL at the time of installation to check the usage. Also note that this link works only on Internet Explorer and not on Mozilla Firefox. Please bookmark this link.