Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
If the breasts are of abnormal size that attracts people's attention or causes unbearable harm, then you may undergo the surgery to remove them. Hanging down or flabby breasts are not normal features of males. Thus removing it is not considered as changing the Creation of Allah.
Allah knows best.