double deductions - twice!!!

My son made a booking through Travelstart on Turkish Airways on Friday. He has a limited monthly spend allowance on my account. He received an SMS confirming that it had been authorised. He later got an email from Travelstart stating that his credit card had been declined. When he enquired, the bank said this was due to the transaction being requested twice! The booking was therefore cancelled. He tried to re-book on Monday and the price had increased by almost R2000! Again the same thing happened where the transaction was approved and then was again submitted a 2nd time which was then again declined. The bank again confirmed that this is what had happened. His booking is about to be cancelled. If I use my credit card to try and confirm the booking the same might happen again. I have therefore borrowed money to make an EFT and hope that this will now get captured. Through this I have been charged an extra R2000