Defective sport trampoline

I purchased a sport trampoline on 3rd November. My husband weighs 55 kg and I weigh 50 kg. In the middle of Dec one of the bungees snapped that held the jumping platform to the frame. After countless emails , Takealot refuses to refund/credit the item saying that it was damaged and not defective. Not sure how one can damage a sport trampoline by jumping on it