Withheld funds

I purchased a flight ticket on Friday the 15th of September 2023, the card was charged immediately. Today 20th September I get debited again. I called the airline customer service and they requested for the back statement, when i download the statement the transaction of the 15th nolonger showing then I called capitec and the consultant tells me it is withheld and she needs me to send the letter of authourity from the airlines that one transaction failed. Honestly this makes no sence because as the bank how do you need the authority from the third party when you are the ones who didnt approve the transaction? Now Im inconvinienced because the airline cant help me without the bank statement and the bank says the airline has to draft aa letter of authorisation.