Irresponsible service

I'm writing this with a huge disappointment.<br> On 26 Oct 2015, I made an online purchase for ZAR 1354. By mistake I made the purchase thrice. Hence, I requested FNB to reverse the first 2 transactions. However, FNB reversed all 3 transactions. Yesterday, there was a debit of ZAR 1427 with the same reference as the transactions that were reversed. I understand that the debit was rightful from the merchant's end. However, the transaction amount has exceeded by ZAR 73. Why did FNB reverse the third transaction, while I only wanted the first 2 transactions to be reversed. FNB is highly negligent in servicing the customer. Now I have to contact the merchant who is in USA, to get this sorted. Highly annoying. FNB makes a mistake system expects the customer to sort of the consequences. And the customer care executive who I spoke to was very rude. The system had technical issues on their side and she was not ready to accept it and kept me waiting, which exhausted my airtime.