Harassment by Standard Bank over closed account

I have been harassed by Standard Bank for the last few weeks over R50 that is outstanding on an account that was closed months ago.

I have confirmation from on of their agents via email that the account was closed yet they are still debiting the account and now state that I owe them money and have gotten lawyers involved. They are also phoning numerous times daily even after I have told them I have no account at Standard Bank as mine was closed.

I am sick and tired of their tactics. Sort your poorly trained staff out Standard Bank!!