What is the ruling on the money that was deposited into the questioner's account: must it be returned to the bank, or is it permissible to dispose of it, especially given that the questioner performed a refinancing operation (debt restructuring) not for the purpose of obtaining money, but rather to ascertain his credit status, and he tried to cancel the operation, but the bank deducted the first installment and fees, and finalized the operation on him?

If the financing was usurious, then you erred in requesting it, and you must repent to Allah and exit this prohibited transaction as much as possible. If you can cancel the financing by returning the money to them without paying interest, then you must do so, in accordance with the Almighty's saying: "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." However, if you cannot cancel it, or if returning the money does not cancel the interest, then you are not obligated to return the money; repentance suffices for you, and you may benefit from it.