Shipping Act Article 23

Any vessel carrier engaging in domestic and international liner service shall collect freights against the fare list which was mentioned in paragraph 1 of the previous Article; however, preferred fares provided by both parties are excluded.No vessel carrier may unreasonably discriminate against passengers or consigners.
中文原文 航業法第23條
船舶運送業經營國內、國際固定航線客貨運送,應依前條第一項備查之運價表收取運費。
但運送雙方訂有優惠運價者,不在此限。
船舶運送業對乘客或託運人不得有不合理之差別待遇。

English translation for reference only; the Chinese text prevails. Not legal advice.