Poor service from Nedbank

Nedbank advised that they sent me communication however I have never received it. A manager whose details I have but will not publish called me to advise that Nedbank has confirmation that the communication was sent to me however the confirmation cannot be shared with me. I don't understand this as legally I am entitled to any correspondence between the bank and myself and since Nedbank is calling me a ****, I think that I am entitled to the information. The Manager advised that she will escalate this matter to the complaints department who will contact me. This was over 2 weeks ago. I have not received any feedback regarding this issue to date.