BSNL Broadband — excess usage bill

sir
my phone no is[protected] and address (a-12, heera baug co-op housing soceity, sussen cirlce tarsali raod, vadodara-390009, guj.)and i have been using braodband facility from past few years. the problem is recent billing for past two months for april and may when all the phone lines were under repair and the phone was hardly working. sir we have paid april months bill for Rs. 12000 appx... which was due to downloading but this month no downloading was done neither netsurfing was done on excess to get a billing amount of Rs. 16000 appx. sir please kindly help me out with the issue we have to pay the money without any usage n the amount is also not small enough to let it go so please sir kindly help me...
thanking you...
your's faithfully
meenakshy singh.