As far as I know one can dispute a credit card transaction. However, if the receiving party can proof that it was you who transacted that it will not be reversed. Of they fail to do that (e.g. fail to present the slip you signed of a normal transaction) then it will be reversed.

I normally pay TELKOM online with my credit card. A few months ago it was duplicated by Telkom and taken off twice. I filled out a dispute form and they said if I am proven wrong I have to pay a fee (R80 I think it was). Then later the bank also wanted a fee which they did not disclose before. Then they reversed both transactions and reprocessed the one. They just could have reversed the one to get same net effect. I never paid any fee after I told them that I refuse as it was not my fault at all. I already wasted my resources to have it corrected...

Not sure how it would apply in your case of an online transaction. You made the transaction in error. Website had some error with the currency unless you selected China as your home county. Tit for tat? I wonder what would have happened if the "wrong currency" was worth less. Then you would have gotten a very cheap flight I guess.