Overcharging on credit card

This has happened more than once now and over time<br> <br> I try to book flights but it says payment declined. Last time I complained I was told it was the bank's fault for declining me but you refused to give me evidence this happened. This time I got wise and phoned the credit card company as I tried to book and they said no request had come through. Other bookings are working, it's just your site. Meanwhile I have to pay you hundreds more due to your error - I call that theft! I also call the first incident lying.