how i block users from using torrent

Hi There,

Thank you for reaching us, If the user's machine has already a Sophos endpoint installed on it, You can use Web Control Policy and block the Torrent on their system. You can navigate to Endpoint  protection > policies > Web Control > (select your existing policy thats' being used) > Settings > (Look for Acceptable web usage) > (Categories likely to cause excessive bandwidth usage>  set peer to peer as block. 
Let us know if this helps you answer your query.