Yes, your employer can fire you at any time. You did not explain, your city or area from which you belong and if you are from USA then I explain you a term "At-Will" employment used in U.S. labor law for contractual relationships in which an employee can be dismissed by an employer for any reason (i.e without having to establish "just cause" for termination), and without warning. When an employee is acknowledged as being hired "at will", courts deny the employee any claim for loss resulting from the dismissal.