This is not correct. Scheduling can change your schedule with early report assignments as much as they want until 12 hours prior to the start of LC, OR until the pilot acknowledges an assignment. If they assign a rotation two days out, and you immediately acknowledge it, that is then locked in. Any further changes require them to notify you, which they cannot do since you are in rest up until report. In this case, since you acknowledged it, you are only required to report for the acknowledged rotation. At that point, since that rotation is gone, you would have to call them and they would then be able to notify you of the rotation removal. You should then go back on LC because any further assignment requires 18 hours notice.