Transaction charges

Hi! I made an online purchase of $250.49 with my GBP account and has debited £198.60. The exchange rate at both the purchase and completion dates indicates that $250.49 is £192. Why have I been charged more? I thought there were no fees. I am trying to get an answer from support team for 3 days now with no success. Very disappointed!!

What time was it in the UK when you did the transaction? Was the screenshot taken at the same time of the purchase?
In principle:

  1. When markets are closed in the UK there could be a small markup
  2. The exchange rate fluctuates during the day
    Finally, are you sure you didn’t allow the POS machine to convert the USD in EUR by itself?