Refusing access to management after poor service

I made a purchase from HC on 14/10/2020. My first instalment (took 6mnth instalment plan) was due end Nov 2020. I however made substantial payment on 24/10/2020 and only later realized I was about R102.00 off from the total cash price. I called them to ask if we could change it to a cash option instead of still paying R900 per month for the next 5 months, but they refused. I told them I'm just short of R102.00 from the cash price, which I was prepared to settle immediately, but they still refused. I ended up cancelling the order completely, returned the goods to them on 28/10/2020 and requested a full refund. I am not even going to mention the lies and the unprofessionalism of their call center staff. Lynette Maliwa tried to explain why it is impossible for them to change the transaction to a cash payment. I requested to speak the head of the department in customer care, but he was never available. I asked for his contact details, but was refused same. Lynette Maliwa promised to get his "permission" to give me his detail and call me back with it. I have been sending her mails and following up, but I get no response. What business would not allow you to communicate with their management? With an average rating of just 1.38 in 4650 reviews, I am not shocked anymore at the level of non-service. Disappointing customers seems to be their way of doing business. I wonder how long I will wait for my refund!