I've seen too many people get in trouble, not ask for their rep, and get fired. Then, they go to worse paying jobs to avoid the union, because they feel betrayed.
Please please please tell everyone that the minute you're called into your bosses' office, ask for your rep or steward.
I don't want to lose any more co-workers for dumb shit because they don't know their rights.
I always have my steward with me when I'm called into the manager's office