D.C. Code § 34-702
If any public utility or any agent or officer thereof shall, directly or indirectly, by any device whatsoever, or otherwise, charge, demand, collect, or receive from any person, firm, or corporation a greater or less compensation for any service rendered or to be rendered by it in or affecting or relating to the conduct of a street railroad or street railroad corporation, common carrier, gas plant, gas company, electric plant, electric company, telephone line, telephone corporation, telegraph line, or telegraph corporation, or pipeline company, or to the production, transmission, delivery, or furnishing of heat, light, water, or power, or the conveyance of telephone or telegraph messages, or for any service in connection therewith than that prescribed in the public schedules or tariffs then in force or established as provided herein, or than it charges, demands, collects, or receives from any other person, firm, or corporation other than one conducting a like business for a like and contemporaneous service, such public utility shall be deemed guilty of unjust discrimination, which is hereby prohibited and declared to be a misdemeanor and unlawful, and upon conviction thereof shall forfeit and pay to the District of Columbia not less than $100 nor more than $1,000 for each offense; and such agent or officer so offending shall be deemed guilty of a misdemeanor, and upon conviction thereof shall be punished by a fine of not less than $50 nor more than $100 for each offense.
D.C. Code § 34-702