Praise be to Allah, the Lord of the World; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
As you know dealing with usury-taking banks is not permissible in Shariah. For more details, please refer to the Fatwa:82049 and 81349.
Therefore, whoever has committed that sin should immediately turn towards Allah, making sincere repentance and giving up that malpractice. If one gets interests on his money he must get rid of it either spending that interest in the social welfare of Muslims or giving it to a needy person.
Allah knows best.