Write a letter to the Employer to convey a grievance.
I am writing to raise a grievance with you. As you are aware that the issue is being considered with regard to the following circumstances (explain the facts and dates, etc.)
I would like to inform you that I am entitled to a hearing to discuss this matter; and also, if I wish, I may be be accompanied by another work colleague or my trade union representative.
Kindly reply within (---) days of the receipt of this letter.