Is it permissible to transfer money between countries via banks for a commission or a fixed percentage (sometimes reaching 20%) deducted from the transferred amount, knowing that this percentage is imposed by the bank and is not an agreement between the two parties, and does this fall under usury (riba)?

If a person transfers money in their country's currency to a bank account in another country, and the account holder delivers the amount in cash to whomever the money's owner designates, and the account holder stipulates a known percentage for this service, then this transaction is permissible and free of usury, as long as the account holder takes a fee for delivering the money in cash.