It's either the ISP problem, user problem or server
problem.
For ISP problem, you have no choice but to bear with it.
Same for server problem. If you don't need the files urgently,
download them a while later.
User problem wise, please check for spywares, adwares and viruses.
Some spywares love to send emails back to some unknown server,
taking up bandwith. If you are using torrents, please limit it. P2P
uses a lot of bandwith too.