Refused to pay money they owed me 😕😡

I did cash back at one of the Supermarkets and I received a decline slip. I got notification from the bank and it showed that the transaction did actually go through, I checked on my App and also did a bank statement and it also proved that the transaction did happen and the figures never lie when I went to the bank without them even checking the bank statement said they will do an investigation and the guy **** that the money was paid back to my account and I told him it shows in the bank statement that they never retained that money. The guy told me they will di an investigation and that investigation said they returned the money but till today i never received that money. It frustrate me that I once wrote a good service review about this Bank. I would never advise anyone after this experience to bank with standard bank coz i can never trust them with my money.