Very Unhappy Standard Bank Customer

I am very disappointed with the service I received from Standard bank Randfontein. I went into the bank on the 20th of February 2018 to pay my Vehicle Installment . I paid R2550. I did not have my Account nr with me and they used my ID to search for the account. I've made the payment and left the bank. A few days later someone phoned me to inform me that the installment is still outstanding. After investigating they have realized that they took the money on the wrong account. On a Credit Card account I had over 10 years ago and which has been closed. Now I m battling with Standard Bank to transfer the money to my Vehicle contract. I even spoke to the branch manager who did nothing to help me. The correct acc is ********** 6 Vaf acc . I need them to sort this out as soon as possible.