Originally Posted by Arsene Wenger

Select “Change reservation” then select the “Cancel this trip and use the value toward a new trip”. Don’t worry as it doesn’t actually cancel anything yet, you get to start a new search with your original trip still on hold, so you’d then re-search for the same dates/itinerary you want and it’d give you the current price for it and it’d display the “cost” difference. If it’s now less the miles/credit you’d be getting back would be displayed and they would be deposited back into your miles balance/wallet once you confirm you want to purchase that new ticket with the funds from your original one.