BSNL Broadband — First Bill

I took a broadband connection , I am residing at Chrompet Chennai, I opted for 500 C+,
I was shocked to recieve my first bill , which mounted to Rs 4906 , inspite of own modem,
Though under the plan 500 C+, I cannot surf 24 hrs the internet. So my usage came to around Rs 3100 apart from this they have charged monthly rent for my first 20 days broadband usage 11nth Aug to 31st Aug, Other charges Rs 400.
So , apart from usage , we have to pay monthly rent for broadband, this is I was not aware .
No proper explanation or guidance for choosing plan