Claiming money owed not willing to assist with statements

I have had a Woolworths account for years. I paid off my full account end September. Since then naturally I have not received any statements.

In December out of the blue I start getting sms's that I owe R154,loggend into my account online, could not see any account statements, checked my email didn't receive any statements, spoke to customer care still don't have any statements. Today I was called by a very rude gentleman saying that I had to pay irrelevant if I have a statement or not, failing to still send me a statement. How can I pay for something I honestly don't understand? I have paid cash ever since my account was paid up. Thus I need to understand where and when this transactions took place and stop the account. No help from Woolworths just threats and sms's