FNB is inefficient

I have been a client of FNB for many years, mostly because I have been happy with their service, well until recently. I had an incident in April were I made a purchase at a store and received an sms that my payment was reversed. I then called the bank to confirm and the Call Centre Agent confirmed the payment did not go through. I then made another payment to the merchant the next week, only to find out that the previous payment had gone off. This was around 17 February 2018. I then called the bank , including my banker since I am in private banking(useless at this point) to get the second payment reversed. FNB has been sending me from one corner of the earth to the other. They requested that I sent them a dispute form and proof that I have tried to get the merchant to pay back he money. I have sent the same dispute form three times and sms indicating my conversation with the merchant, still no resolution on the matter. I am currently looking to move my accounts elsewhere where I will get better service because I find this ridiculous and *********** at best.