Administrative Regulations on Amateur Radios Article 27

The call sign of an amateur station shall be assigned by the competent authority on the issuance of the amateur station license. However, the call sign may be assigned directly by the competent authority when the application is made for establishing a temporary station.No amateur operator shall be allowed to request the assignment of a certain call sign. However, the competent authority may assign the call sign as applied for when the call signs of the special amateur station and temporary station meet the requirement of Article 28 and this does not cause duplicate assignments.When having obtained the qualification for a higher class, the amateur operator may apply to the competent authority for changing the call sign for the originally established amateur station.Once the call sign of the aforementioned amateur station has been reassigned, the old call sign shall be returned and shall no longer be used.
中文原文 業餘無線電管理辦法第27條
業餘電臺之呼號,由主管機關於核發業餘電臺執照時指配。
但臨時電臺得於申請設置使用時,由主管機關逕予指配。
業餘無線電人員不得要求指配特定呼號。
但特殊業餘電臺與臨時電臺之呼號符合第二十八條規定及無重複指配之虞時,主管機關得依申請指配之。
業餘無線電人員取得較高等級之資格後,原設置之業餘電臺得申請改配呼號。
前項業餘電臺呼號一經改配,原業餘電臺呼號予以收回,不得再使用。

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