Some iPhones are easier to unlock than others, depending on the carrier and the phone’s circumstances. Most iPhones purchased within the past year will actually be unlocked already, but if your iPhone is older, your mobile phone provider may be able to unlock the phone for free, or you might find that you’re able to unlock your iPhone yourself.
You’ll discover that your iPhone has been locked to a particular network if you insert a SIM card from another network into the iPhone and attempt to make a call. If it doesn’t work, it’s likely that your iPhone is locked to your network. You might see an error messages such as “Invalid SIM,” “PAYT Lock,” “SIM Card Not Accepted,” “Enter SP Code,” or “Insert Correct SIM Card.”
Don’t forget that the iPhone 4S uses a MicroSIM, which is bigger than the iPhone 5, iPhone 5S, iPhone 5C, iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPhone SE, iPhone 7, and iPhone 7 Plus so be sure you’re using the correct sized SIM.
Unlocking your iPhone is completely legal if you purchased the device unsubsidised or have finished paying for your contract. However, if you’re still paying for your contract, you technically don’t own the iPhone yet, so you really should check with your carrier before unlocking it. Here, we’ve got a list of popular UK carriers and how to go about getting your iPhone unlocked by them.
Updated on 1 August with general updates.