Not refunding defective products

In Feb I bought 2 whiteboards, but when they arrived, they were defective. I returned them and Takealot replaced both. Unfortunately, they were also defective, so I requested a return. The courier collected both. Takealot however, only refunded me for one. I've re-logged the return numerous times, spoke to so may support staff, but every time, they just mark the issue as concluded without any feedback. I have bought many things from Takealot, but this is the last time they will see me as a customer.