Is it permissible to take the amount of a debt that its owner does not repay from the usurious interest of a bank?

You have done well in your intention to stop dealing with usurious banks, and you must hasten to do so, for Allah Almighty says: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger. But if you repent, you may have your principal - [thus] you do no wrong, nor are you wronged." And usurious gains are ill-gotten wealth that should be spent on the general welfare of Muslims, such as orphanages and for the poor. It is not permissible to take from it in exchange for your own money that you do not expect to recover. So, hasten to dispose of it in its proper channels.