Cab drivers are by law (in much of Europe) required to have their prices stated on the window or inside the car, with surcharges clearly displayed. The driver must also have a valid id and license displayed inside the car.
Are you sure you actually rode a taxi and not some illegal or almost illegal rideshare like Uber which has no such regulations? If I were you I would have taken a picture of the car with the license plate and then reported them to the authorities.
They have all of that. Then you get to the place and they hit some buttons and crazy opaque math happens and then you have a 30 minute fight with the dude. And the reader was always broken and no they can't break a 100 or a 20 or a 5
Up front pricing is way better. When I used to do cabs I'd always do upfront prices. $40 to the airport no meter includes tip. 50 ok sounds good. Let's go.
Are you sure you actually rode a taxi and not some illegal or almost illegal rideshare like Uber which has no such regulations? If I were you I would have taken a picture of the car with the license plate and then reported them to the authorities.