How To Restore Your iPhone
This tutorial is addressed only to those who need to unlock their iPhone and use an unlocked phone.
Of course, you can use the tutorial if you have an iPhone locked to a network, or you have the SIM of the phone operator that you want to use the phone and remain on the same network.
Connect your phone to your computer via USB cable, open iTunes, select your phone from the left, then click “Restore”.
iTunes will ask if you want to make back-up to your phone first. Caution! If you had jailbreak, iTunes will only save “legal” files that were not installed by the jailbreak community. If you want to keep your files, contacts, photos etc, press the “Back-Up” button;
Click on “Restore”;
Required version of iOS will be downloaded after the restore process will begin. Following is the reset phone;
Once the phone is activated, you will see the option to restore using your backup previously made. Choose the saved backup file, and then click “Continue”. What I recommend, however, is to select “Set up a new iPhone” to have a “clean” restore.
If you had a jailbreak before, after you make restore using this tutorial, no one will be able to realize if you had a jailbreak or not, even if you select to do the back-up restore.
Your phone will reboot, and then you can start to use it.