IPHONE 5S DAMAGED GOODS

TWO MONTHS AGO GOT A CONTRACT FOR AN IPHONE 5S AFTER 2WEEKS OF GETTING THE PHONE IT OVERHEATED AND I TOOK IT TO SOUTH GATE MALL CELL C STORE BUT THEY NOTIFIED ME THEY DO NOT HAVE A TECHNICIAN ON STORE I SHOULD GO TO THE GLEN ISTORE EVEN THOUGH I GOT THE CONTRACT WITH THEM . SO I TRIED TO CHANGE THE CONTACT BUT THEY NOTIFIED ME THAT I CANNOT TO THAT BECAUSE ITS STILL NEW ... NOW THE PHONE IS NOT WORKING , IT DOE SNOT RESPOND WHEN I TOUCH SCREEN ITS JUST ON ONE SCREEN . I DO NOT KNOW WHAT TO DO I AM FRUSTRATED WITH CELL C . I NO LONGER WANT THE PHONE HENCE IT IS DAMAGED GOOD WHICH WAS PRE OWNED . IS THIS HOW CELLE C TREATS IT CUSTOMERS ? ARE WE NOT VALUED AS CUSTOMER BECAUSE THEY DEBIT VERY MONTH WITHOUT FAIL WHY CANT THEY DELIVER A GOOD CUSTOMER SERVICE