Regulations for Applying and Allocating Telecommunications Numbers Article 7

The telecommunications enterprise and those which have been allocated with special telecommunications numbers should cooperate with the competent authority to adjust the telecommunications numbers it has been allocated.When the users of telecommunications numbers proactively return the allocated telecommunications numbers, the competent authority may abolish part or all of the allocated numbers after reviewing and determining the compliance with the relevant provisions of these regulations.
中文原文 電信號碼核配及管理辦法第7條
電信事業、獲核配特殊服務號碼者,應配合主管機關調整其所獲核配之電信號碼。
電信號碼使用者,主動繳回其獲核配之電信號碼,主管機關經審酌符合本辦法相關規定後,得廢止其一部或全部電信號碼之核配。

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