“Find My iPhone” needs to be disabled before you sell your phone.
If you don’t have access to your iPhone or it will not turn on, you can disable “Find my iPhone” through iCloud. Here’s how:
1. Using a desktop or laptop computer, go to iCloud and sign in to your account with your Apple ID and password. You must use the same Apple ID and password linked to the iPhone you’re selling.
2. Click the Green Icon “Find iPhone” See picture below.
3. a Map will open up on your display. Then click “All Devices” right at the top of the screen in the centre.
4. Select the device you’re selling.
5. A new window will appear displaying the iPhone you selected.
6. Please click on “Erase iPhone”
7. Now there is just one last step left. iCloud will show you another message as to the picture below. Please click “Remove”
8. That’s it!