It has been brought to our attention that you have violated company policies on multiple occasions. [Company Name] has a strict policy regarding [describe the specific issue(s)]. When you first began working for this company, you signed a statement agreeing that you would adhere to the company's policies; you have failed to do so.
It is extremely important that all our employees follow company policy precisely. This letter is a written warning to remind you that this type of insubordinate behavior will not be tolerated. Any further disciplinary action may result in the termination of your employment.