Liable for interest after my account is paid up

<p>On the 17th of May I called in to enquire about a settlement debit order the person I spoke yo said they couldn't debit the account bit I had to make payment @ the store for me to be able to settle my Rcs account he then said the charges will stop being added on once the account is paid up yesterday I paid the balance on the account and I called in 26th of May to have my account closed the agent i spoke was rude and shouting @ Me as I had problems with the fact that there was all of a sudden R20 interest on the account , which I knew nothing about I checked the Balance before I settled my account and was under the information the account is on a 0 balance, after arguing back and forth and being spoken to like a 2 year old the call was escalated to Ncumisa confirmed same story, why must I pay the R20,When I was told something different when I called in?whose fault is it that the agent I spoke to told Me the charges wouldn't be billed when the balance is paid up?I'm not paying a single cent toward the account again as the slip I got shows 0 balance, their people need to learn how to speak and explain how the accounts work to us as Customers. I want to close this account and I want nothing to do with Rcs and their rude staff as this is not the 1st time I've encountered such behavior.</p>