Is it permissible for someone who borrowed pounds to repay them in dollars?

A person goes to a financial institution and they lend him, for example, one thousand pounds, and they tell him: "We are giving you a bond for these one thousand pounds valued in dollars, so if you come back after the value of the pound has dropped, we will increase it for you in dollars?"
If he borrows something, he is entitled to what he borrowed; he must return it to him at the time of repayment, or its value, just as the Prophet (peace and blessings be upon him) said: . So if he borrows a Lebanese pound or a Syrian pound, at the time of repayment he gives the same currency if it is still in circulation, or its value at the time of receipt. It is not the time of taking it from him or buying it; no, he returns its value at the time of repayment. So if the repayment falls between them in Muharram, then when Muharram arrives, he gives him the pound or its value in dollars or in a currency other than dollars. There is no harm in taking it at the price of the day. He said: "O Messenger of Allah, we sell for dinars and take dirhams, and we sell for dirhams and take dinars." He (peace and blessings be upon him) said: .