Service going down the drain

Ii was charged twice on my credit card for a single transaction! I am not sure if this is the fault of the merchant or not. I filled in a dispute form once I became aware of the double charge and have not received any feedback from FNB. When I followed up on my dispute I was told that the matter was escalated and I would receive feedback within 48hours! This did not happen. I then attempted following up again via the fnb app on messages and I was referred to an agent by the name of Xolani who was completely impatient! I gave my reference number but he still wanted me to tell him whether it was for a dispute or credit card. His question made no sense. Then he again rephrased and asked if it was for a credit card or debit card dispute. He just could have used my reference number and assisted me but he did not do this. He almost ends the chat because of his lack of patience to wait for my response! He finally just stated that the matter was escalated. But this was the same response a received a week before ! Completely unacceptable…. Why does FNB allow this kind of treatment to clients by their employees??? It’s noteworthy to mention that I also contacted the merchant who has indicated they are still investigating. But my own bank does not help me recover my money

This is not all. On Friday the 21st day Of July I received my credit card balance which was completed over stated by Atleast R20000 and I wonder if this is how FNB then calculates interest on amounts which they have incorrectly, thereby overcharging customers!!!