FNB WON'T LET ME PAY SMART DEVICE FROM ANOTHER BAN

I wanted to close my FNB account due to the fact that they refused to grant me a credit card so another bank gladly approved it. They then refused to close the account as they claimed because I have a smart device account I have to stay with them. I then mentioned that I'm prepared to pay the intalment from my new account & still they refused. Now I'm forced to transfer funds every month into this FNB account I'm forced to stay with.....as a result, by the time the funds reflect they had already returned the debit order due to the fact that my pay date & the debit order date are the same ie. 25th. Even when the funds reflect the next day they don't want to recollect the debit order again & so I'm forced to incur additional unpaid debit order costs. Why don't they take their money because now I'm getting threat SMSes that legal action will be taken. I'm really disappointed in FNB's service....really.