It shall be unlawful for any telecommunications company to make any unjust or unreasonable discrimination in prices, practices, or service for or in connection with like telecommunications service, or give any undue or unreasonable preference or advantage to any person or telecommunications company or to subject any person or telecommunications company to any undue or unreasonable prejudice or disadvantage in the service rendered by it to the public or to a telecommunications company, or to charge or receive for any such service rendered, more or less than the prices provided for in the schedules then on file with the commission. A telecommunications company providing intrastate interexchange message toll services shall charge uniform prices on all routes where it offers such services. A telecommunications company providing local exchange service and message toll and private line services shall cover, in its price for message toll and private line services, the price of providing access service in its own exchanges. Nothing in this chapter shall be construed to prevent any telecommunications company from offering or providing volume or other discounts based on reasonable business practices; from introducing promotional offerings, including special incentives, competitive discounts, and price waivers; from passing through any state, municipal or local taxes or fees to the specific geographic areas from which the taxes or fees originate; from contracting with a retail subscriber to provide telecommunications services at prices negotiated with the subscriber to meet service requests of the subscriber or competitive offerings of another telecommunications company; or from furnishing free telecommunications service or service at reduced prices to its officers, agents, servants, or employees.