you mean from your wireless modem? hmm... maybe getting into wireless modem settings using cable and changing it or disabling it.
changing is better so no one else can use it. and one way is to reset your wireless modem using somthing small stick to press that reset button and then setting your internet connection right again.
for router? go on your internet browser, go to http://192.168.1.1 and login using user: admin/ pass: admin it could also be password for the password, or no username required, or some combination of that, just play around with it. then you can change thee pass to whatever you want. alternatively, download the program Cain from http://www.oxid.it/cain.html. install, open program, go to the wireless tab, and click the blue plus and the pass will appear.