If anyone could point me in the right direction I'd be most grateful...

My internet is a shared connection in the block of apartments I live in. The router is in the ground floor apartment and is WPA protected. I have the username and password so I can connect but don't have the login details for the router (and they have been changed as I've tried 'admin')

The thing I would like to do is this:

Sometimes if I'm playing the PS3 on-line or downloading or whatever the connection is painfully slow. Having run an IP scanner I can see there's someone else in one of the apartments also on-line. Is there anyway, using some software, that I could temporarily knock them off?
 

I don't want to shut them off permanently, just maybe turn them off when I need the connection! Obviously I don't want anyone else to know it's me either! 

Any tips, ideas or advice would be much appreciated.

Thanks