476.5  Adherence to schedules — discounts.
  No public utility subject to rate regulation shall directly or indirectly charge a greater or less compensation for its services than that prescribed in its tariffs, and no such public utility shall make or grant any unreasonable preferences or advantages as to rates or services to any person or subject any person to any unreasonable prejudice or disadvantage.
  Nothing in this section shall be construed to prohibit any public utility furnishing communications services from providing any service rendered by it without charge or at reduced rate to any of its active or retired officers, directors, or employees, or such officers, directors or employees of other public utilities furnishing communications services. Provided, however, said service is for personal use, and not for engaging in a business for profit.
[C66, 71, 73, 75, §490A.5; C77, 79, 81, §476.5]