I currently has a reservation already booked with 2 passengers on the reservation, for a flight say Oakland - Baltimore for $139

There is "1 seat left" reduced price right now of $99 (if searching for two passengers the price is still 139, and if I do a fare-change for my current reservation it says no price reduction because two people are on the reservation).

Is there any way to get the price drop for one person stored as a future travel fund which doesn't involve cancelling the current booking?