Unauthorized charge

I have an issue with regards to an online purchase I made in April. Order was placed on 23 April and payment went through on 28 April. Got my order delivered and all was okay (except for 1 item that they did not have stock of). On 12 May they refunded the full amount back into my bank account, and on 13 May they took the full amount out of my bank again. Thought it was strange, but because they took their money again I assumed it wasn't a big deal. Now on 14 August, they again took the full amount for the same purchase out of my bank account. I have now done everything I could possibly do from my side. I contacted the company, they say they went through their books and statements and they do not have any payment from me (only the one from April, which was a legitimate order). I personally went into the bank and filed a dispute for the charge, was told it would take up to 10 business days to resolve. Today is business day number 11 and I have not had ANY feedback from FNB. I tried to do ask about in on your chat, but was transferred twice. The third agent I spoke with, said I must give a few minute so that they can view the previous communication. After 30 minutes of not responding at all, this agent dared to ask me what my issue is about! I was livid and asked to speak to a manager. I was told I would hear from a manager in 24 to 48 hours. Well guess what, nothing! I have sent a reply on the email the agent at the branch sent to the dispute team. Only for them to respond and tell me that they are not the correct department. I have waited more than 2 weeks. Could they really not respond on the day the email was sent jus to say it is the wrong department? I have no idea what else to do. I am out of R1065 and FNB is doing NOTHING to help me!