Nightmare trip from New Zealand to Johannesburg

I have sent several complaints (in writing) to various addresses on the Qantas site complaining about my experience on 6 December 2018. I now got a response to say "sorry - these things happen" we hope you have a better experience next time! Not acceptable! I had a nightmare trip from NZ to SA. We were up at 02h30 in the morning to drive to the Wellington airport for a 06h55 flight. We received no sms to say the flight was delayed. On arrival we were told it would be delayed by an hour. This carried on 3 times until we were delayed by 3 hours. We were concerned about our connection at Sydney to JHB as there was only a 3 hour delay. There is only one flight a day. We asked staff who told us they would wait for us. We landed in Sydney at 11h35 and our flight to JHB was due to take off at 11h35. On disembarking we found our plane was still on the ground but the gates had closed. There were 20 passengers in the same boat. They left without us. We then spent a nightmare of a day - with no explanation or apology from the airline staff. We were handed a sheet of paper saying we were put on a flight to Doha. I was travelling with my granddaughter and refused to take what would have been a 40 hour trip when I had paid good money to fly on a 19 hour trip. That's when the fun started. They told me if I didn't want to go to Doha I had to sit on the side and wait. We waited for 4 hours. We had not eaten since breakfast that morning. We were then ignored. Every time I got up they told me to wait. Eventually at around 16h00 I threw all my toys out the cot. I had sat there crying and visibly upset. We were eventually put on the flight the next day (which I had been told a few times was full and I could not go on). We were sent to a hotel over the road which meant we had to fill in a whole batch of forms for a Visa. We eventually got to the hotel at 18h00 - booked in - had room service and slept. We went to the airport the next day only to have yet a further delay on our flight to Johannesburg. I sent a 3 page letter to Qantas and was told these things happen. If I wanted to take 2 days to get home - I would have taken an Emirates or Singapore flight which is 35 odd hours and much cheaper. My flights every year cost between R62 000 and R82 000 for the 3 tickets as I take my granddaughter to see her father in NZ. I have always had 3 or 4 hour delays on one or more of the legs - but this was very stressful and upsetting for me and my family. To travel with a child you take the quickest possible route and get this result? In previous years we have waited for people on that connecting flight - for over an hour - and we were already on the plane! Why didn't they wait for us? My granddaughter was supposed to start flying unaccompanied from the end of this year and now she has refused to do so - which means I have to take her again this year. This whole experience has been a total nightmare! I expect some sort of refund on my tickets. Nothing less!