66 Pa.C.S. § 1304: Discrimination in rates.

No public utility shall, as to rates, make or grant any unreasonable preference or advantage to any person, corporation, or municipal corporation, or subject any person, corporation, or municipal corporation to any unreasonable prejudice or disadvantage. No public utility shall establish or maintain any unreasonable difference as to rates, either as between localities or as between classes of service. Unless specifically authorized by the commission, no public utility shall make, demand, or receive any greater rate in the aggregate for the transportation of passengers or property of the same class, or for the transmission of any message or conversation for a shorter than for a longer distance over the same line or route in the same direction, the shorter being included within the longer distance, or any greater rate as a through rate than the aggregate of the intermediate rates. This section does not prohibit the establishment of reasonable zone or group systems, or classifications of rates or, in the case of common carriers, the issuance of excursion, commutation, or other special tickets at special rates, or the granting of nontransferable free passes, or passes at a discount to any officer, employee, or pensioner of such common carrier. No rate charged by a municipality for any public utility service rendered or furnished beyond its corporate limits shall be considered unjustly discriminatory solely by reason of the fact that a different rate is charged for a similar service within its corporate limits.