Why my serial number for a product that has been replaced
Hello,
I bought a New IPhone 5S, 16 G, System Version 8.4.1, Sales Region : HKSAR
from online site, after i received it, i found out the touch screen is hanging every time i lock the device for 10 mins for example and when i unlock it it hang won't slide i try three or four time until the touch respond, then i start to hear a weird sound inside the device like little thing moving inside, so i wanted to check the warranty check for my device, i found out this ( We're sorry, but this is a serial number for a product that has been replaced. Please check your information and re-enter your serial number. If your information is correct, you may need to contact us.)
How is that my Serail Number is Replaced, whats the new Serial number then ??
iPhone 5s, iOS 8.4.1