Normally they are like, AMEX, diners, some credit card that supports wildlife stuff.. other ones I cannot even recall.. the not 'normal' VISA or MasterCard.
WELL ANYWAY! Upon walking through town to the train station on my way to work one day, I decided to be polite, smile to one of the guys &got lured into his speil.
HIS ULTIMATE MISTAKE [&loophole for all future encounters!] was when he asked how old i was. I think at the time, i was 22? Maybe 23? He said 'oh sorry you have to be 25 for this card.'
Every. single. time. since then, anywhere I see any of these places, they try to lure me over, I say 'sorry not old enough!' and keep walking.
Works like a charm.
[Also, try 'I'm a student.' which translates to 'sorry! i has no moneyz!']