Ongoing bank charges on a closed account

I have been dissatisfied with the service I receive from Standard bank for a few years now. I closed my account in March of this year - I went into the branch on Chatterton Road and signed the relevant documents and I was told that the account was closed. I have since received monthly statements and was recently called by a consultant who queried why my account was in a negative balance. Despite the consultant assuring me that he would make queries about my account closure and rectify the matter I yet again received a statement today.