Poor Service by the FNB.

The FNB staff has been dragging their feet on my query for a refund of funds they've written back to their own account when they closed off my late father's bank account. I've submitted all the necessary information and documentation since October 2024, but they do not want to refund the money and they're not giving any valid reason, at the branches, they do not want to take responsibility for this poor service as they put blame on the head office and estates business unit. I need assistance to get the matter resolved.