Closed account

I have an issue where I had to close my FNB account (Got a home loan offer from another bank and had to move my account) My company paid money into the closed account. We thought that FNB will send the money back to my company in order for them to pay me into the correct account.

I contacted FNB and they told me to go into the branch, but I cannot understand what the problem is.

What can I do to get FNB to pay back the money?