BSNL — Internet Data eater !!!!!

Sir, I am using mobile since 8-9yr & regularly using internet -5-6, I always put my data pack on, but today morning suddenly data was finished, when i checked its shows as 770mb was used @ 8.45am, i didn't even using mob @ that time, its really impossible :(, i am really v v upset, every one telling that its my prob, when i didnt used mob how can it go like that? ( they are advising to off data when i am not using, this is the 1st time this kind of non-sence thing is happening, i never thought u ppl also doing like this!)