I just booked a flight on the TAP Air Portugal website and the fare was €78. When I got to the payment stage, I put in my credit card details and my bank sent me an SMS verification code, which is normal for the credit card I was using.

I have an Australian credit card and, interestingly, the SMS from my bank stated that I was trying to pay AUD135.59 (not EUR78) to TAP. But at no stage was I asked if I wanted to pay in AUD - throughout the entire booking process, the price was shown in EUR. TAP simply converted the amount to AUD without asking, and with a mark-up too. (And yes, these SMS codes normally do show the currency that the payment is being made in - I got one just before showing an amount in EUR for an Iberia booking.)

I decided to pay via PayPal instead, which gives the option to pay in EUR or my home currency, and ended up paying EUR78, which worked out to be AUD130.76 when my bank converted the currency.

I suspect quite a few people would not notice that TAP is doing this.