Hey, Citibank charges me the "convenience fee" when I use my Citibank ATM card at a Citibank ATM outside the US!!!! AFAIK, most all US card issuers do the same for any charge outside of the US, regardless of whether it is in local currency or USD.

P.S. Just because a scam also exists outside the UK doesn't make it wrong to report it in this forum if the OP has only encountered it inside the UK.