If you are called into a meeting with supervision for discipline or for discussions which might lead to discipline, you have the right to union representation. You as the member, must request this representation. It is not management's burden or obligation to offer you a representative...it is the member's responsibility to ask for it. Under the Weingarten rights, you can read the following statement, if you are called into a meeting:
I have reason to believe that this investigatory interview may lead to disciplinary action against me: therefore, in accordance with my rights under Federal and State statues, I respectfully request that this interview not begin until
(1) My Union rep is present
(2) I am advised of the subject and purpose of the interview, and
(3) I have had opportunity to consult with my Union Rep.