Unauthorised transaction put through

I tried to pay for a flight via my credit card, but the secure transact system was offline and thus I only received my OTPs after 4 hours (having logged off and paid cash instead). I received a phone call from ABSA ***** to ask whether I wanted to reverse the transaction - I affirmed that I did not authorise it. Yet the transaction went through. I phoned the ***** line again who referred me to the Authorisation branch, who could not assist me as I'm not a merchant. I played phone tag for an hour with various ABSA consultants who could not help me. How can transactions that are not authorised get processed? My card is currently maxed out as I'm paying for things I did not bargain on.