Forgive me if this has come up before. I recently made an online work-related purchase from a UK company and used my personal credit card details by mistake instead of my business card. Within minutes of placing the order, I realised my mistake and phoned the supplier who said that they would immediately return the amount (about £250) to my card and took the details of my business card. Everything went well and the goods were received but, when I eventually got my personal credit card statement, it correctly showed the same sterling amount going out and back in on the same day but they used a different exchange rate for each transaction, leaving me short €13. Not a large amount I know but I am a bit annoyed about it - can they do this?