MTNL Triband billing problem

I am using MTNL triband connection last month i was out of station only 15 days i used internet and for that MTNL charge me Rs. 950 bill. Then i went to the MTNL office ask about details. They told me we charge you as per your usages. and one think they told me that if your router is on and your PC is off then also you will charge. That means switch off your router before shut down your pc.

Yes there is lot's of problem in MTNL triband but don't have idea about that if your router is on and your not surfing then they will charge or not.

I am using unlimited plan so no problem about billing. I am getting correct billing and speed also good.