Holding Charge
 

Has anyone had a holding charge placed on their credit card when booking a flight with United?

Last summer I booked flights and was double charged for them. The airline admitted it was a mistake on their part and rectified the matter.

Last week I booked more flights and the same thing happened. Upon contacting their customer support I was informed it was a holding charge placed on my card and that this was a 'standard business transaction'

I have never had such a 'standard business transaction' for any other purchase on my credit card. They've messed up and refused to admit it.