overdraft Facility debit without informing client

I am a nedbank client for close on 15 years and a private bank client for more than 5 years with Nedbank Fourways. As a private bank client I am charged a monthly fee above banking fees and interest etc etc for the services of a private banker and a more personalized relationship with the bank. on Monday I noticed my overdraft access facility was no longer available and R20000 was debited from the cheque account. Upon follow up with my relationship banker Rhea Singh at Fourways, she advised me she had no knowledge of this and investigate. More than 24hrs passed without any response , requiring me to follow up twice even though I pay for services of a private banker who has no idea of what is happening on my acct. I was informed after 48 hrs from the query and follow ups that this action was taken by the credit manager -Ronelle. As a client surely I deserve the courtesy of being informed before such a decision is taken to act on the account. To date nedbank cannot prove correspondence to this effect, not provide contact details of management to rectify. I am yet to receive the level of urgency and service that I am billed for the past 5 years. It's time to move banks.