FLIGHT BOOKING AN ABSOLUTE JOKE!

My PA used my sky miles to book a flight and paid for airport taxes using my credit card. The payment was accepted through the system and we received a booking confirmation. We phoned a day or 2 later to request a quote if we would want to change the flight (we didn't change the flight). The call centre agent however could not find the ticket in the system and my PA specifically asked if I would be able to fly if she cant even find the ticket and she was assured that I would, only to find out on the Saturday, upon trying to do an online check-in that the ticket had been cancelled due to an incorrect credit card number. We had no notification of this cancellation. How is this possible?? This is totally unacceptable.