I had an issue with b pond this week, looked at my download...

I had an issue with b pond this week, looked at my download meter and saw a huge spike for one day,i know i was'nt on comp that day so sent them an email asking for explanation,reply was we don't know what was downloaded we only have info that so many bytes went to your modem,could hve been an auto update on your comp,yeh possible but how can i know for sure, the data has come thru their system, if thats true how can iinet know what there customers are downloading?