Bsnl 500c problem in usage update

[chin]

I have 500c plan of bsnl. I have installed auto-shut down software installed.It shuts down the computer exactly at 7:55 a.m.Now the problem is even if the software shuts down the computer at 7:55 a.m i have been charged extra 70mb(displayed on regular usage)But the thing is i cannot terminate modem connection.Power,dsl,internet lights are ON but only lan1 light is off but there is no downloading taking place. still there is download and upload displayed from 8:00 to 8:23 a.m.i terminated the modem connection around 8:20. Is it necessary to terminate even modem connection??. if i'm on the pc i would have restarted the modem.This happened twice.