Issue with a Takealot order

Am having an issue with Takealot and I don't know how to proceed. I buy a lot from them and this is the first time something like this has happened. About 4 weeks ago I purchased an Amazon Fire. I was having a problem logging on so I returned it. They told me that there was nothing wrong and they would not replace it.

I said great, fine, but could someone please show me what I am doing wrong. This is my 4th Fire, so I couldn't understand what I was doing wrong, and apparently it had been looked at by their technical department. That was 2 weeks ago. I have written to them again on several occasions asking them what I should do next, but no reply. I really don't want to cause a fuss, but I want my product returned - if it is working - or exchanged if it not. I don't think it's too much to ask. I have paid for it. My problem is finding someone to communicate with. I have rep**** to their emails, but as I say they are not replying to me. How can I resolve this? It's about a R2k spend so I want it back. Has anyone any ideas please?