Find My iPhone is part of the Find My application ... can provide the original proof of purchase that matches the serial number of the device. Apple’s policy is to protect against device theft.

You don't need to press the call button; your iPhone's IMEI number will instantly appear on the screen. Alternatively, you can find the IMEI number by opening the Settings app and going to General ...

You may need to know the serial number of your iPhone if you're unlocking it through your carrier, having it serviced, or selling it. It's easy to locate, but figuring out exactly how to find the ...