Unhappy customer due to FNB having loop holes in their systems

On the 8th of July 2021 i received a call from FNB’s higher in charge . I was given the same feedback i received 2 months ago. That my money (a total of R16 500) could not be refunded. On the 10th of June 2021 i received a liable letter from the bank stating that i accepted an OTP and that is why the money could not be refunded. Today when i was contact i was told that i was right. No OTP Was accepted and that some message was sent to my cell phone which gave them confirmation that i accept the payment . I told the person i was speaking to over the phone that FNB is. Ow changing the story and saying that no OTP was send when i was sent a liable letter confirming that an OTP was accepted. I have given nobody permission to make a purchase from my bank account and have accepted no message to allow anyone to make this purchase . I have noticed that many people are experiencing the same problem as me . Clearly there should be some loop hole within FNB’S system. Furthermore i have spoken to so many consultants at the ***** department who have promised to contact me back. But yet failed to do it . The type of service the bank provides is ridiculous as nobody can resolve the problem. I was told that a good will gesture can be given to me of R4500 . This amount doesnt even come near the amount that i have lost.