How to make 3 roles in windows form?

Google Translate:

I am making a program for an Internet provider with a database, a program with authorization and registration, there are roles, login and password. The roles are admin, client and service department. There was a problem - I don’t know how to separate the roles so that the admin can change everything in the program, the client can only order goods, and the service department can mark the completion of the order (work done). Be so kind as to help with advice.
There is a class with roles, but I don’t understand how to make 3 roles, not 2.

public class checkUser
    {
        public string Login { get; set; }
        public bool IsAdmin { get; }
        public string Status => IsAdmin ? "Admin" : "User";
        public checkUser(string login, bool isAdmin)
        {
            Login = login.Trim();
            IsAdmin = isAdmin; 
        }
    }