You can do iphone 4 unlock if you want to unlock your iphone. If you have an older iPhone that has been disabled, don't just throw it away. Consider "jailbreaking" and unlocking it for free. You can replace the SIM card with a pay-to-use card and use the iPhone for international travel or a backup phone. Even if the iphone4 is disable you can still use it if you are going to unlock it. You can unlock it for free by looking on the internet.
Here is how to unlock iphone 4 disabled. Look in the phone-information section of iTunes to see what type of phone and what version of system software you are using. Do not upgrade your software version without first checking that unlock iPhone4 software exists. Refer to the jailbreak matrix to see what software will jailbreak your phone and specific version of firmware. Then, download on the the jailbreak software on your computer. Follow the installation wizard, which will guide you through jailbreaking your IPHONE4. The process can take about an hour.
