You mean your iPhone got locked after you connected iTunes and updated?Then, the unlock would have been a temporary one..and hence when you updated the firmware the network lock got returned.To unlock an iPhone the remote unlock service would be a better option because, you need not give your mobile to someone else nor do you have any chance to enter the wrong unlock codes. To get such an unlocking service for your iPhone 3G approach Theunlockarena.com and by submitting the country and network to which the mobile is locked to you will be able to remove the restriction from the respective network. This will be a permanent unlocking solution.