I'm wanting to know what is using up the bandwidth.  Is there any way I can see what is using the most?

My nephew plays runescape A LOT - and my sister is constantly complaining that the internet is slow.

They are only on a small plan (3GB) but within 10 days of their billing cycle rolling around they have used .75 GB over their limit and are reduced to dial up speeds.

I'm looking around for better plans - but I'm worried that my nephew playing runescape is just going to suck it all up again.

Help please.....