The best way to solve this problem would be to hide your SSID (Your wireless networks name). This stops anyone who has a wireless enabled device i.e a laptop, pc, games console, e.t.c to see your wireless connection.
In order to do this you must first connect to your router by typing either the default gate (Start>Run>type in CMD) and a black prompt box will appear (if running xp, if not type in command) the in the prompt box were the cursor flashes type "ipconfig" this should give you the following IP address, subnet mask and finally your "default Gateway"
Type the numbers on your web browser (Internet explorer, Firefox, Opera, Netscape, Safari e.t.c
Once you get access of the routers homepage you should see a wireless option, click it and you should be able to see an option "Hide SSID". You may be prompted for a "User name and Password" by default this should be admin/admin of admin/password e.t.c unless you have changed it.
Once you do so, nobody will know you have a wireless connection.