I need my refund back

On the 23rd of February 2025 I went to Engine garage also known as Beaufort convenience centre in Grahamstown to fill up my car as I was paying with a card loadshedding happend as the machine was processing and then the attendant said the transaction didn't go through there was also no slip that said decline as I asked for the slip I didn't get the slip. I had to pay again because the first transaction meant I didn't pay and then the attendant assured me that the money will be reversed back to my account the next day. The next day I went to the Garage with my bank statement I asked for the manager explained to him what happened he took my statement checked it and made a copy he also took my details and the 4 last digits of my card number. He promised to check for the transactions and call me as soon as possible. He did not explain to me how the process usually goes since they deal with such incidents, he just told me to go to my bank. I went to my bank and the lodged a query with the 2nd slip that I received from the attendant. The message came back from my bank that both transactions are no longer with them but with Engine garage. I then went back to the Manager and showed him a new bank statement as for the first one the monies were pending and on the second one both of the transactions went through. The manager now says they received one transaction on thier side and they gave me a slip stating that of which I went to my bank again they sent the proof from the garage and the message came back saying the money is no longer pending at the bank. The manager is adamant that they only received one transaction of which it cannot be as the bank shows proof that the money is with them. I need my refund back please help