Nedbank do bad business.

Nedbank is reducing my overdraft on my business account, month by month, without any discussion or contact with me. After the 2nd secure mail I sent them, somebody finally came back to me to discuss it. She took another week to come back to me regarding what their credit department had to say. She then said, "The credit department says they will continue to reduce the overdraft as we tried to contact you and send you a letter". They have reduced my overdraft by over R5000 already. Does this sound like good business practice? I've had my business accounts with them for 17 years, but am moving elsewhere.