When you need to purchase iPhone, you should take the following steps to verify its originality.
Step 1: Find the serial number: Dial the code *#06# or on the phone go to “Settings” > “General” > “About” to display the serial number. Then,
Step 2: Go the Apple website through this link https://checkcoverage.apple.com/ke/en/ then enter your iPhone serial number. If the site shows the code is invalid, then your iPhone is not original.