BSNL broadband Inrenet connection
Excess billing for the month of August

I am a subscriber to BSNL broadband connection under the HOME 250 plan. My regular usage bill doesn't exceed the basic amount. In august I wad billed for usage of Rs.2655 in addition to the minimum charges. My complaintof 25-Sep was replied stating that "Broad Band usage throughout for the above period is from the same port and PC only", without mentioning the usage details. When asked for the details I was told that the same can be viewed from the bsnl port, which when I log on displays the message FORBIDDEN ZONE. Kindly advise me on this.