My iphone's serial number says its a returned product.

Hello there i bought a iphone not too long ago and it was working fine until one day it randomly started to restart so i thought it was broken so got another phone, now today i thought what the heck why not see if theres any warrenty left on the phone to get it repair or replaced which is when i found out it said my iphone was a returned product which got me thinking was this a returned iphone to the store thats been sold on by apple to sell?

I also have another strange one, when i plug my iphone into itunes it comes up saying its a iphone 5c which i thought it was but when i checked the imei and serial number against websites to see if i had cleared the icloud because i was planning on selling it on ebay as faulty it pops up on everyone of the sites saying its a iphone 5s??

Now i asked some people about this googled it found nothing, asked a mate of mine who owns a shop to look inside it to see if it was a iphone 5s motherboard inside a 5c case, it wasnt the screen connecter was indeed the one for a iphone 5c.

So my question is what kind of mutant phone have i got???