iPhone does not have an unlock code, or any type of sequence. It is officially unlocked on Apple servers, which means that even after updating the system or making a factory reset the device will stay unlocked.
In order to unlock an iPhone you need to provide the IMEI number, which can be found by dialing *#06#, or by checking in the iPhone settings.
Second thing is to provide the correct network for unlocking.
You always remove the blockade from the network in which the iPhone was bought, not the one that you will be using in the future.
If you don’t know the network you can use iPhone network finder.
Network unlock for an iPhone doesn’t use a code or unlocking sequence. The device is remotely unlocked on Apple servers.
There are two types of instructions for iPhone.
1. Insert a simcard from a different network than the one working in your device.
* the unaccepted simcard cannot ask for a pin code at the start. Please use a simcard that doesn’t ask for a pin, or turn the request for a pin code off.
2. Start the device and turn on Wi-Fi
3. Small update should be downloaded.
iPhone is ready to work in any network.
Second option (if the Wi-Fi option doesn’t work)
1. Connect iPhone to the PC by cable with an unaccepted simcard insterted (simcard from a different network than the one where you bought the device)
2. Start iTunes application on your PC
3. Small update will be downloaded.
iPhone is now network free.