Unfair refunds procedure

On the 23 April 2021, I tried to purchase six tickets. My selection for the tickets was 09h00. Due to their site being problematic there was no confirmation sent to me. Apparently this sale went through, with no reference number issued to me. The system kept displaying error messages. I tried again to book the same flight but the third time around I got a message stating that specific flight was sold out. I further tried to book the next available flight which was for 17h05. I managed to receive a reference for this one. Even though this flight was "booked" their system kept reflecting pending. I had to call them and hold the line for ages, at some point I opted for the option to be called back. Eventually I was assisted and the money was allocated correctly. When I went to check my booking, I noticed the date was wrong, had to change the date to the correct date, I was charged a further R2400. On the 27th April 2021 at 09h00 I received an SMS alerting me that my flight was open for check in. When I opened the link sent via SMS, I noticed the reference number was different, that was the first time I was seeing that reference number. I called them to enquire as per usual I could not get through. When I finally got hold of them in the afternoon, I addressed my concerns about the ticketing errors, the lady that was assisting me made me hold for a while claiming that she was speaking to her supervisor. Their final response to my concerns was that they will refund 85% of the money I paid for the tickets and they will issue R300 voucher per person for the changes I made. Till today I am still puzzled why I will be eligible for 85% of my money. The error was on their system!!! Why am I paying penalties? Why are they refunding me with vouchers if I had made an error with the date? I will never recommend anyone to use this airline. They are ********. I want my full refund. I don't even want their vouchers because I'm not planning to have anyone I know use this airline. I want my money. This has been the worst experience ever. Only on the 27th April 2021 I got a call back from them stating that I asked to be called back. This was the option I opted for on the 23 April 2021. Wow such incompetence!!!!!