Originally Posted by jsloan

This is undoubtedly the correct approach and the only way UA is likely to get this fixed quickly. When they see the number of successful chargebacks shoot up, they'll investigate. Successful chargebacks are expensive for the merchant.

Credit card companies have a specific dispute category for overcharging -- "I agreed to pay $X and they charged me $Y." The fact that everyone in this situation has a receipt that shows the correct amount should make this a no-brainer with quick resolution.