The O2 page at https://www.o2.co.uk/help/device-and-sim-support/unlocking-an-o2-mobile-to-use-on-a-different-networ... states "The easiest way to unlock your device is in My O2:
However, I can't see a "More" in the menu bar at the top of the page! Although I have an account I no longer have my O2 locked iPhone 4 registered.
As advised by an O2 shop, I've tried phoning 0344 809 0202, Press 2, Press 1, but can't hear a subsequent option to unlock the phone.
Please, how can I unlock my phone?
That would be dependant on you using that phone as your main phone for a while @Jessie1234.
As you no longer use the iPhone you need unlocking I will see if the community gurus can help.
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here