FNB HOME LOANS LACK OF RESOLUTION SINCE FEB 2024

I have raised a query with FNB home loans through my private banker and to date I have not had any resolution. My FNB home loan has excess funds in it and over the last 3 debit orders my prepaid funding/excess funds has reduced and nobody at FNB can provide me with a concrete logical answer or proper mathematical formula as to why this savings portions is reducing over and above my monthly debit order. I am now looking to move my bond and accounts to another bank.