Complaint and threat from Manager at Engen garage

On the 18th of June 2020, I asked the petrol attendant to pour R150 petrol and he poured R150.06 and swiped my card without consulting with me regarding the 6 cents which i did not have in my account. The transaction declined as no funds available. I told him that there is R150 in my account and im not sure why its declining. He asked me to try again then i checked on the screen and noticed that i was charged 6 cents extra. i informed him that i dont have the extra 6 cents he has added on my bill. He then advised that he will ask the ladies at the till to remove the 6 cents and charge R150 as i had initially requested. The transaction declined again. i therefore asked the attendant if they are charging me for all these declined transactions and he confidently answered, NO our machine does not charge for a declined transaction. so i tried for the 3rd time and it still declined. i therefore went to their ATM to check my balance and i also checked on my standard bank application first. Their bank charged me R8.50 EVERY TIME WE SWIPED AND MY CARD DECLINED, WHICH WAS 3 TIMES (R8.50 X3=R25.50). So i was left with a balance of R124.50 in my account. So i withdrew R120 that was available. i informed the service attendant that they have been charging me and because of that my balance is less. My argument is that i asked for petrol of R150 BUT WAS CHARGED R150.06 and because of the 6 cents extra that was added without my consent it lead to the transaction declining and more charges on my side. The assistant manager was very rude and refused to even listen to my side of the story and wanted me to pay the balance. I tried explaining and showing him the proof but he walked away being very rude. the petrol attendant that was helping me therefore went to explain to the manager and i was informed that i can pay the R120 and come back tomorrow and pay in the balance once the R8.50 gets reversed back to my account. So that never happened and i never went back to the garage. i received a call today from *** on 29.06.2020 from the garage and i was asked when am i coming to pay the R30. I informed the guy that the R8.50 was never reversed back into my account as they thought it would. As we were speaking, there was a man on the back round, swearing and threatening of how he wants the money. I therefore asked to speak to him and was informed that he is the manager. i asked him why is he screaming, shouting and threatening on the back-round as that is very unprofessional. He did not even know the scenario that took place but just wanted his money. he kept on swearing and informed me that i do not know him and he is coming for me. Please advise what do i do with such a terrible service. I expect the garage and i to come with a solution that is fair on both sides and i want that manager to apologize for threatening me. ENGEN (ROBERTVILLE) SIYABONGA CONVINIENCE CENTRE. ***