Except as otherwise provided by this Charter, the salaries of the department heads of the administrative departments of the City shall be set by the Council in the annual City budget, but shall not be changed during term of office under any appointment. Subject to the civil service provisions of this Charter and subject to budget appropriations, the salaries and remuneration of subordinates and employees of the departments of the City government shall be set by the head of each respective department in accordance with any pay plan adopted by the Council.