Closing Discovery credit card is a nightmare

I have been trying to close up the credit card with Discovery. It's been a nightmare. I paid it up and paid more and they still refused to closed it. Saying that they owe me R30 and they want to pay me back and I called to say I don't want it they must just close it. They still didn't close it and that was yesterday, 10 August 2018. Today 11 August 2018 they still refuse to close it claiming that I owe them R20 what happened to them owing me. That is why they don't want to close it, they wanted to keep it so I can owe them for life. I wouldn't advise anyone to take credit cards with them, they rob people. Better do it straight with FNB, the service is the best there.