Credit card query

I had a credit card with FNB and later found out it was a product linked to Discovery, the card has been closed however still appears on my FNB internet banking profile. I erroneously made a transfer into the closed credit card and contacted FNB to assist with the reversal of the funds but I have been sent from pillar to post. I was told to contact Discovery which I did and they could do nothing about it and they sent me back to FNB, it’s been several months and still no resolution. Can someone help please