Woolworths Financial Services: Shockingly poor service and negligence - avoid credit cards from them!!!

As longstanding customers of Woolworths, my wife and I decided to get the 'Woolworths Black' credit cards last year. Having been accustomed to the excellent service that we normally receive from the Woolworths food stores, it was a shock to encounter gross incompetence and negligence in the financial services business. This began when we went into the store in Cape Town to get our cards, a process that took hours (despite us having all of the relevant documents and information) because the staff were not properly trained. Our usual practice is to have the full outstanding amount debited every month from our credit cards, ensuring that there is no interest payable. We set this up at the inception of the cards but it was not implemented by Woolworths. To our dismay, they started charging us interest on our account. Okay, everybody makes the odd mistake - we then phoned them to address the situation. They assured us that the debit was now set-up. Wrong! They proceeded to do the same thing again, which forced us to keep topping up the account manually. Without any prior notice, due to their own failure to debit our account, Woolworths then got a debt collector to contact us asking why we had not paid the outstanding balance!!! My e-mails to Woolworths Financial Services requesting repayment of incorrectly levied interest have received zero response on this subject.