Transaction Reversal

Couldn't get reversal money for transaction that went through from my account but not to Merchant and I ended up paying the Merchant using mu African Bank card. Now they're telling me that they can't help me. When I spoke to their FNB 3D department and I was told the amount that was taken should be reversed but from their side they can't see it. Why don't they do their job and speak to all relevant department to solve the problem