oh well that is easy.. download this program here. its called ziphone
http://www.ziphone.org/ .
this is kinda tricky but not really all that hard. what you will need to do is force the iphone into recovery mode. to do that hold both the home button and the sleep/wake button until it shuts off. continue holding the buttons until the ipod turns on and shows an itunes logo and an ipod/iphone cable. then let go of the buttons. now open up itunes and restore and upgrade the iphone to 1.1.4 once that is done restart the iphone and reconnect it and open up ziphone... once open there will be a button that says DO IT ALL... that will jailbreak and unlock the iphone to use any sim card you like.. that process shouldnt take more than a couple minutes. once everything is done you will need to go to the new app on the iphone called installer and find and install BSD subsystem. that should do it for ya