There are cloistered nuns and secular nuns. Secular nuns who live in the community as teachers, social workers, nurses, etc. do get paid. In the past it was standard practice for a nun to give her salary back to the religious order in exchange for room, board and a small living allowance. These days, with more members of religious orders living alone or in small groups, traveling, etc., I don’t see why a nun shouldn’t have a credit card.
I understand all the words, they just don’t make sense together like that.