Tex. Rev. Civ. Stat. art. 4013a
No steam or electric railway company, street railway company, interurban railway company, or other chartered transportation company, express company, sleeping car company, telegraph or telephone company, shall directly or indirectly, by any special rate, rebate, drawback, or other device or exchange, demand, charge or collect or receive from any person, firm, association of persons or corporation a greater or less or different compensation for any service rendered, or to be rendered, in the transportation of passengers, property or messages, than it charges, demands, collects or receives from any other person, firm, association of persons or corporation for doing for him, them or it, a like service, if the transportation or transmission is a like kind of traffic or service under substantially similar circumstances and conditions.
Tex. Rev. Civ. Stat. Ann. art. 4013a