Credit Card does not work

FNB's ***** department blocked a online transction and the only feedback to me during the transaction was "Incorrect Card number" which was obviously not accurate as I got an approval request on my app. They did not notify me in any way of suspicious activity on my card. When I contacted FNB support via the app I was first told incorrectly that I must have entered the card number incorrectly, and they hand no record of any attempted transactions. Which only after I pointed out that if this was the case it would not ask for approval on my app they referred me to another department which could find find the transaction and advised that it was blocked by the ***** department. No reasons were provide and I was asked to send a seperate request to a seperate email. The only response I received from said email that they will reply within their SLA, without providing any information as to what that SLA is. So the result is I cannot transaction on my credit card I pay for, and I have no indication when and if that will be corrected