Fnb is the worst

I have a credit card with Fnb. For the past year I have been paying it and not using. Money is in my account every month. This morning I get an sms stating that they didn't receive my payment and that I must pay an amount of R329. I noticed last year they didn't the same thing as well. Money is in my account they took the money out last month. I see bank charges being added onto my credit card when it isn't my fault. This is utter bull****. Fnb takes out the money whenever the payment is die but what happened during this month. As I have mentioned I've been paying this for the last year and it still isn't paid off as yet and I haven't been using this. Is this fnbs new ploy to robbing people..... Really sick of this