MTN - Broken process and service

I recently upgraded my cell phone contact at an MTN store in Klerksdorp at the La Piazza Square, that evening while I was using the phone and setting it up, I noticed that a pixel on the screen looked defective and I returned the device the next day, they couldn't give me a replacement device, even though the consultant could see the defect herself. They said if they returned the device and gave me a new one, and if the returned is not defective, the consultant will be liable to pay for the device. How does that work? Really crazy process and I had to fight just to get the device returned. I now have a new contract, but no cell phone. What the hell MTN. Where is the customer service.