If you buy an iPhone from another person and try to switch out the SIM card and use it with your current provider you may be shocked to find out that it is locked. Then you will ask someone if they can show you how to unlock my iPhone 4. This is not an illegal practice and it is rather simple to accomplish. You just need to jailbreak the phone to be able to use it on any network you want to. You can do this directly from the iPhone using its built it browser.
On the iPHone 4, open the safari browser and go to a site that is host to the software JailBreakMe 2.0. Once there the screen will display a notice that will say, “Slide to jailbreak.” Simply slide it from left to right. You will then have to wait just a few seconds before another dialog box shows up that informs you that the jailbreak has completed successfully.
Now you will need to reboot the iPhone 4. Hold the sleep button down for a few seconds until another slide bar displays the instructions to “slide to power off.” Slide it from left to right. This will turn the iPhone’s power off. Now you can press the “sleep” button to power it back up. The process is complete and you can use the iphone on any network.