Bad service

I need help or advice to where should I report my case, I bought car parts at Hyundai Durban CBD branch on the 14th of November the transaction went through on my side but to them the slip came back with an error message saying that there was an online error, ok on the following day they asked me to go to my bank and ask them to reverse the money, I did and my bank made a correction and I received back my money, I then immediately went back to Hyundai to buy again since money was on my account the transaction was successful. On the 17th I received a payment from someone but when I checked my balance the available balance was zero, I was so confused until I checked account balance thats where I saw a negative balance of the very same amount I paid at Hyundai, I phoned my bank the bank said the money is with Hyundai they processed two transactions the one that declined and the one that was successful. I went to Hyundai with my bank statement on the 18th they promised to sort this thing on Monday, on Monday I waited for their call and money but I did not received anything, on the 21st which is yesterday around 16:00 I drove to speak to them, on my way I received a call from my sales man telling me an issue has been sorted I should expect my money early in the morning today, I waited today until 16:00 I phoned them but no one was interested to answer my call they kept on transferring my call until I decided to go there personal, when I arrived there they started to call their bank and send them my documents no one came to me and apologise I was sitting there watching them busy scanning the documents I gave them on the 15th... Then after some time I saw a guy coming to me and asked me to follow him to his office, when we get there he apologized and told me I am not going to get my money they are doing investigation since on their side they don't see my transaction, he asked me to go back to the bank, I refused and we had a very big disagreement. My question was to him why did the sales man call me and promised me my money while they still investigating? What investigation are they talking about because the statement shows the reference of them deducting my money? Why am I the one who suppose to suffer as a client, my time waisted coming to them, my airtime phoning them with no answer, my petrol travel to speak to them several times, my debit orders being desputed due to insufficient funds on my account after I got paid?

No one gave me any explanation instead they said to me I must give them again my bank statement and ID copy to submit to their bank.

I need help please what steps should I take