BSNL Broadband
Snl bills Rs.40000/- per month for broadband.. But usage shows only 3G

I am currently using bsnl broadband for 6 months. All very nice upto the last month. Today I received my bsnl bill for broadband use.

It is around Rs.40000/- and I am using HOME500C plan and I only used 2981MB.

It is total wrong billing by BSNL. HOW TO REGISTER A COMPLAINT ABOUT THIS IN CONSUMER COURT?

WHAT PROOF I NEEDED TO FILE A CASE AGAINST BSNL. I MEAN EVEN THESE COULD CHANGE THE DATA WHEN I FILE A CASE AGAINST THEM.

HOW COULD I PROOF THIS LEGALLY AND SUBMIT TO CONSUMER COURT.

THANK YOU...