To be able to use it on any cell phone network you will have to know how to unlock an iPhone 4s. Once the phone is unlocked there is not a restriction on the SIM card. This frees the phone up to be used on any network which uses a standard SIM card. Make sure that the phone is already jailbroke before you start the unlocking process.
After the car is jailbroken, you will have the “Cydia” app on the phone. Open this app and then search for a program called “ultrasnow.” Once you find this software program install it on the iPhone 4s. After it has been installed, reboot the phone by pressing both the home button and the sleep button at the same time. Hold these two buttons down until the screen on the iPhone goes black and then the Apple logo appears.
This is the fastest and easiest way to unock an iPhone 4s so that you can use it on any network you choose. You should now be able to switch out the SIM card with one from the provider you would like to use instead. It should be completely unlocked so that cell phone providers are available for using.