Bad service

I paid my Mr Price account in full two months ago and called to cancel my account immediately. I spoke to a very rude lady she didn't even ask my details she just told me that it was cancelled. March I received a statement telling me I owe R5 I call in to ask why another rude lady confirmed that it was cancelled yet I received a statement for April saying that I owe R5. What makes me angry is the part that I closed my account with a credit balance and all of a sudden I'm owing someone better make sure my account is closed