When a person buys an iPhone, they create an Apple ID and Password (Lock Activation details). When done, the iPhone locks itself to this identifier information. This is for security reasons; only they know the Identifier/Lock Activation details.
Scenario: Person buys a USED iPhone that is left locked by the previous owner, that is, the iPhone contains the previous person’s iCloud Activation Lock details – their Apple ID and Password.
Problem: How to unlock it?
Answers:
Way 1: Ask the previous owner to disable the Activation lock from their end
Click ‘Find my’ button and select ‘All Devices’ and then select the appropriate iPhone
Click on ‘Erase iPhone/iPad’ and then click ‘Remove from Account’
Way 2: Ask Apple to Remove iCloud Activation Lock for You
You can either Call Apple Support or Visit your local Apple Store.
If the iPhone is new:
You will need to show that you own the phone, i.e. proof of purchase showing the serial number of the iPhone and your name.
If the iPhone is second hand:
If you’ve bought a used iPhone, you will need to show proof that ownership was transferred to you from the seller. You will have to provide the sale transaction receipt/proof of payment.
Way 3: Use Third-Party products?
Be careful when choosing third-parties offering unlock services. Some may try to exploit vulnerabilities in Apple’s operating software. Be careful when choosing.
The following is a list of third-party unlock services: