Please guide me for bsnl billing system

Can bsnl charge for the period their broadband is not working ? I mean for last three months the service was deactivated by bsnl, even incoming was not available. Is there any clause where the waiver of rental for the period when the bsnl didnt provide the service is achieved. Please answer

Have you given any written application ? Usually waiver given for telephone connection/sIf telephone rental is waived, same applied for BB rental also.