BAD SERVICE

I have problem with FNB credit card, I have a credit card of R12 000 limit and my due date for the minimum payment is the 27th, I always paid my credit monthly not even a single month I ever skipped paying it, I open it in 2005, in January I did make a minimum payment of R1074 as I was suppose to before the due date on the 25th, that was I always do.to my surprise the next morning the 26th my account was debited to pay credit card again for the same amount R1074, I immediately called the call centre I spoke to about 5 people until the last person told me that I must wait for 3 days in order for a reversal to be done as it was a mistake on their side and she even confirmed that my due date was the 27th and that I have infact paid double I wanted to use the money and as soon as it reflect I used it, and then I received an SMS that my limit has now been decreased to R11 500, no explanation and no one never bordered to call me, today I received another SMS saying that I now exceeded my limit and that I need to pay R836.52, I then again called call centre and spoke to Charity she tried to explained to me the reason behind it,i need this to be reversed asap, not my problem.