The itinerary I want to book only has Standard awards available currently. However, looking at near-in dates, they seem to release Saver Awards at the last minute.

If I book a Standard Award, and the Saver Award becomes available for the exact same itinerary, can I just pay the $25 (Premier Gold) and it's considered a change (inside 21 days) or does this require the ticket to be cancelled, miles redeposited, etc. Thus hitting me with the $100 change fee.

Thanks.