Credit Card charged twice in error

Legacy_user

I recently made a purchase via the internet and used my MBNA card for it. The seller charged me twice in error and have refunded me the money. However the purchase was in Euros and the variation in the exchange rate between the time they made the mistake and the time they gave me it back means I am an extra £30 out of pocket.
What recourse do I have with regards to this with the seller and/or MBNA although I don't really see why MBNA should have to do anything at all.

Ms_Chocaholic

A similar thing happened to me when my credit card was used fraudulently on a poker (betting) site by someone in Russia - the amount was credited back to my credit card before I knew anything about it as the poker site recognised the dodgy transaction (my card registered in the UK but the registration on the site being made by someone from Russia).

There was a slight difference (around £10) in my case due to the exchange rate changing between transaction and the refund but I spoke to someone at the credit card company (Capital One) and that was refunded, not a problem.