Refurbished phone sold as new

Purchased a brand new iPhone 6 via contract at the Cresta branch on 29 August 2015.We did not see the device being opened in front of us. Phone was activated. We left the store after purchase. I tried using the device. It started heating up and mic would not work. On closer inspection of the device we saw incision marks between the case and screen of the phone. We took the phone back to the branch on the 30th August 2015. The BM Gordan Mckenzie refused to even inspect the device or give us a new device. He insists on booking it in for repairs. Even shouted at us. We refused this as we did not get what we paid for in our contract. We called the customer service department,they tried talking to the manager and he refused to budge. He even went as far as moving to the back office and saying that the device was dropped to the consultant on the line. We had to leave the store at 3pm.We spent 3 hours in the store. We then took the phone to the Istore and the consultant inspected the phone saying that it was previously opened and therefore not a new device. We have escalated this query and await the response. Poor service from Telkom mobile Cresta branch