Under the Weingarten Rights established by the NLRB and upheld by the United States Supreme Court the following rules must be followed:
Rule 1: YOU must make a CLEAR request for union representation before or during the interview. You cannot be punished for making this request.
Rule 2: Once the request is made the employer must stop the interview/meeting and wait for arrival of the representative or end the meeting.
Rule 3: If your employer denies the request you have a right to refuse to answer any additional questions.
Here is more information about the types of meetings conducted by AT&T and other workplace rights:
Investigatory and Disciplinary Meetings