Overcharged and no plausible explanation

I booked tickets to Port Elizabeth. Paid via credit card. When I received confirmation of the booking, the amount on the confirmation was not the same as the amount I was charged. I called the call centre, the agent just said I was charged the correct amount, and the confirmation was incorrect. I refused to accept this because if they project the amount, I should be paid that amount, whether correct or incorrect. Why should I pay for their mistake. I was asked to send an email to guestcare, so I did. I got a reply fro Shabnam who gave a whole explanation that the web people made a mistake and attempted to explain the discrepancy in the amounts. She said that the VAT was not included in the confirmation amount, yet this was still not correct as you do not come to the amount I was charged. I rep**** to say their calculation were incorrect, and to this day I have got no response. Mango does care about the people or their reputation. Absolutely pathetic service.