ATM Deposit

I was depositing R20,000 in the STD Bank ATM in Northgate (on 4 Dec.2020), the ATM miscalculate the money and recorded R11,700 and gave me back R300, which means R8,000 was not recorded by the ATM. I immediately reported the matter inside the bank. They assured me that they will calculate the moneys on the atm and will record any extra money. I was assured that this issue will be resolved. Today when I finally went to the bank (a week later), they produced all the paperwork from the machine and said nothing about recalculating all the moneys on the ATM. They told me there is nothing they can do that I have lost the R8,000