Strange Logic

Several chains of bank machines in Brazil can recognize foreign bank cards and subsequently ask whether I would like service in Portuguese, English, or Spanish. When prompted, I always chose Portuguese, thinking that this will trick the bank into giving me a preferential exchange rate since, clearly, as a Portuguese speaker, I am not just a tourist but rather someone who lives, works, and breathes Brazil. Although I am not sure what would possess me to come to this conclusion, there's no harm in trying, is there?