MBD does not protect or respect privacy of financial information

I am constantly receiving calls and sms concerning an account owed by somebody else for Foschini. I have tried advising the agents that the have incorrect cellnumer and they need to remove me and they either drop the call or endlessly refer me to different numbers which return me back to the initial number. Can I be assisted of where to report this behaviour of MBD, which organisation can I report them to since they refuse to correct this themselves. When i ask for call records the call is dropped. I have total access to this other individual's details (no use of ID numbers for privacy) including amounts owed. This now needs to be reported to the authorities, it can't be corrd\ect that they treat somebody's personal info with such disrespect. Where can i report them?