Do you have the right to ask a manager to give you a reason for calling you in to have a private meeting?
That is, management has a right to demand your cooperation regarding a meeting at any time for any reason during hours for which you are being paid your normal rate. Management is not required to provide you with a reason for taking away your hours or for your attendance at a meeting.
Good management practices might indicate that it SHOULD tell you why your hours were given to someone else and the reason you are being told to report to a private meeting. But your question pertained to rights, and management is not required to do either of these things.