If you have subscribed for a limited plan like home 500 or home 250 with bsnl broadband you should be very careful in using your broadband, i myself have been over billed many times by bsnl, just because my bsnl broadband usage were sky-high ,and i didnt know how to check my usage .
So here's how to check your bsnl broadband usage:
1.First of all ,you should know what your portal id is , for that dial
1800-424-1600 and ask them what your portal id is ,if you cant get through dial 1957 and find out your local help line number ,and ask them what your portal id is.
2.Go to data.bsnl.in or bbservice.bsnl.in and sign in with your portal id and password ,
3.Then go to My services ,under search criteria , in service name select broadband,account no. -select the number which i given their,and under usage status select unbilled
4.If you have gone to bbservice.bsnl.in,this might be different ,just goto the check usage section and check for desired month
This is how to check you bsnl broadband usage ,next time be carefull about that bill.