Frustrated Client!!!!

I have been a client of FNB for 16 years, and I am so sad to say I am disappointed by their service. On the 29th of September 2022, FNB account a transaction of 479 X 3 went through from RAIN service provider amounting to R2395. with shock I phoned FNB requesting the reversal, and I was told to provide proof and submit a debit reversal form of which I did. On the 4th of October I received an email informing that i must be advised that they need to follow Visa Rules which state that client is required to attempt to resolve with the merchant at least 2-3 times and forward the bank all attempts to resolve. I responded that unfortunately I cannot provide proof from Merchant as I communicated with them telephonically and don't have recordings. I hereby understand the request made by the bank however never in my personal capacity or by my app have mandated the bank to pay without my concern as this was just a once-off transaction that I never subscribed to then I will never get any correspondent from them as I have never subscribed with them I am still confused and frustrated why would such a large and secured brand make such a blunder of paying without verifying the subscription or getting a mandate from their client then will expect this to be resolved without further harm to both parties. on the 5th of October I received a notification of reversal of R479 from FNB instead of R2395 I expected, what happened to the other outstanding money of R1900. I have been trying effortlessly to be assisted telephonically and online but without any help!!!