Before today, if you have a free schedule change, it won't let you reprice until you use up your two free online schedule changes. Today, any free schedule changes older than 15 days won't have the online option anymore so you can reprice or get tricked into paying more when you actually have a free change. This was the way free schedule changes used to work a few years ago where the online option disappeared after a few days.
If the flight in question by the OP has no free schedule change, I have no idea then.