Shockinly Treatment from a Manager at Postnet

Last year I rented a post box at postnet nortcliff. Throughout this period my box was dominated by another clients mail with important documentation. Every Time I collected my mail all the mail not belonging to me was handed over to the information desk where I requested that they resolve the matter. Every Time there was progress on my request. I phoned the manager now and was shocked that she encourage me to go to hello peter , to please cancel my box and talking about the South African Law. I don't care and don't know about the South African law i paid for my box for my use and they did not see it important enough to resolve the matter , what about client service and what have i paid for. Needless to say this manager bads manners, lack of business skills and the encouragement to take my complaint elsewhere. Will this arrogance be the result that she thinks they are the only ones with mail boxes. Does she even know what kind of money my business spent at Postnet for services. Guess not. Would be great to hear what the National Credit Act about the merits of my argument and if i have the privacy when i paid for it. Im stunt!!!