Credit Card account charged with R5999.99

A charge of R5999.99 showed on my account in July and I immediately phone the customer service to reverse the charge and the operator reversed it and advised me to cancel the credit card and apply for a new one just to make sure that the charge does not go through when it is re submitted. I did so and receive a new card a week later and only to find out that the charge went through.I phone the bank again to stop the payment and I was advised to file a dispute which I did and I was hoping that it will be reversed, but it never happened. My card instalment for this month will be a whopping R9392.45 which will be deducted at the end of the month I can't afford it. I can't get hold of the so called supplier which I never gave permission to charge my account-- M* Style and Travels. Why does the bank give credit limits if they allow charges exceeding the credit limit to go through, in this instance the R5999.00 was exceeding the available credit limit at that time.