§ 188. Service charge based on quantity. No person shall impose a service charge which is based upon quantity in excess of the actual quantity of any commodity or article serviced. Nothing in this provision, however, shall prohibit the person or persons rendering the service from establishing a minimum charge therefor; such minimum charge to apply to all quantities up to and including a fixed limit regardless of the actual weight or measure of the commodity involved. In the event of the establishment of a minimum charge, the dispenser of the service shall inform the person receiving the service, by advertisement or otherwise, of the terms of such minimum charge.