Yes,provided the iPhone is not locked with a different network..If it is, then you need to unlock it.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 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.Once unlcoked you can switch over to other GSM networks.