The company started the card transaction without having the ticket

The company accepted my credit card payment and it went to pending. The payment was voided as apparently the ticket became unavailable within the few minutes I entered my information. This feels really unfair, why would they take the card payment to pending if they didn't have the ticket. Now I have to wait for my bank to undo the pending transaction which could take up to 5 working days - I don't have access to £800 of my own money for maybe up to 5 working days because of Fly Sharp's system. Never going to use these guys again, they shouldn't have moved my credit card payment to pending unless they were 100% certain I had the ticket.