my iPhone 5 serial number is showing as a serial number for an iPad mini

i bought my iphone 5 from a friend. and she got from her husband who works in riyadh. the phone was working perfectly fine for 3 weeks when all of i sudden it stop recognizing any sim and showing "no network" went to local apple mac store here in the philippines and was surprised to found ut that the serial number is showing an ipad mini. no sure what happned &%$##@