Cannot stop or reverse unauthorized debit orders

I have experienced extremely poor service from FNB lately. I have disputed a debit more than a week ago and was advised it now takes 5 days for the request to be processed. I followed their process and advised my private banker of the issue ,she reiterated by email their 5 day turnaround time which I waited patiently for with no response , when I contacted them after 5 days I was told that it is now 7 to 14 days I fear that another unauthorized debit will run this month and I have no way of stopping or disputing it ,my only option now is to move my banking services to another bank