It is usually an option in your bank's app. It depends on the bank though, obviously. If it's not there, you have to be vigilant while using your card (always select the local currency when given the option).
I checked and it doesn't look like any UK banks have this option - at least I looked at about 5 different banks websites and all have pages suggesting you always select to pay in local currency but none of them have any information on disabling this behaviour
Gemini confirms it's not a thing, and not really possible (the terminals just detect the country from the card number)
I don’t know a single bank in Europe that provides this option
Edit: Perplexity says this:
> cards cannot block DCC offers because the merchant terminal identifies your card’s country of origin from the card number and offers DCC accordingly. Always manually decline at payment to let the card handle conversion at better rates
My bank (mBank in Poland) has per card options for declining various types of transactions, among others: made using the magnetic strip, with DCC, with added ATM surcharges.
The bank probably cannot disable the "service" offered by the terminal but seems to get enough information to be able to decline the transaction.
shawabawa3|18 days ago
Gemini confirms it's not a thing, and not really possible (the terminals just detect the country from the card number)
noname120|18 days ago
Edit: Perplexity says this:
> cards cannot block DCC offers because the merchant terminal identifies your card’s country of origin from the card number and offers DCC accordingly. Always manually decline at payment to let the card handle conversion at better rates
embe42|18 days ago