I think one time I tried to buy a 72hr pass from the ticket machine with a CC. And IIRC, it didn't go through because it was asking me for a PIN. It was a while back, so I'm not certain. But I did have a problem though. There might be a ZTM kiosk/counter in the baggage claim area. I'm just familiar with the automats outside at the bus stop. Or there could be a manned counter where the underground train station is.