unathorised debit order

it has been several years since i was a client at Nedbank and has not experienced any problem with their service just until recently and im so disappointed in them. since January 2016 until recently i have realized that there is an unauthorized debit order of NRB ACCTING SUBSCRIPTION FEE of R156 and when calling their call centre they told me that they will investigate and nothing is happening so far. i am so deeply disappointed with the bank and consider moving my account to another bank.