(a) On a complaint against a person or corporation owning or operating a pipeline business subject to this chapter filed by any person authorized by Section 121.152 to file a petition and complaint and sustained in whole or in part by the railroad commission, each customer of the pipeline is entitled to reparation for or reimbursement of a rate or charge made or adopted by the pipeline for a purpose relating to the operation of that business, including a rate or charge for gas, service, or meter rental, or in the event of an inadequate supply of gas or inadequate service in any respect.
(b) The amount recoverable under Subsection (a) is the amount paid after the filing of the complaint in excess of the proper rate or charge of the pipeline as finally determined by the railroad commission.