hmmm...your ISP found fault in the connection? sounds vague....
i was thinking more about your router. if it is wirless, you need to create a password..etc. you can get to your router's settings by typing its IP address in the address line of your browser(at least that's how mine works). any smartphone can hack wireless routers to steal your bandwith, and a password is not always enough(especially if it is weak) also, bittorrent software should always be closed when you aren't using it.
if you get to your router's settings page, check the security log
glad if i could help
-skilly
-edit -how am i being unclear?
perhaps you need me to tell you how to find your router's IP address?