BSNL Broadband
Unauthorized use

I have a broadband connection against my telephone number 03772-270433.which is disconnected on dec 10th because it has a huge outstanding amount of bill. I paid the bill of rs 8010/- on 23rd dec. the bsnl authority was reconnect my line on 24th dec. after that i did not use the connection, but on jan 5th a new bill arrived, that was rs 7095/-. how is it possible?

so, I think that it is unauthorized used by somebody. I want detail bill of its usage.

Thanks