Fnb bank reversal problem

Yesterday on the 22 November 2024, I made an instant payment transaction to my standard bank credit card. Everything was fine when I was busy with an EFT transaction. I even verified the card number was correct. Even on the last stage when the system prompt me to confirm, the first six digits and the last four digits of the card were correct. To my surprise after the payment went through when I receive an email to confirm the transaction, I noticed that one number which is digit 12 is incorrect. I immediately chat with them and they confirmed the number for me. I was surprised to find out that digit 7- 12 are completely different from my card number. Remember those are the numbers that doesn't appear when the system prompt me to confirm. So the consultant sent me the reversal form. However I feel that I should reverse it immediately because it looks like someone has played with the system. It was already late for me to print the form. Big Question ❓ Why only the hidden numbers were incorrect? I verified my card number 100% ..who tempered with the system. Why the bank don't do immediate reversal to save me?