If I book an itinerary for 2 people say, myself and boyfriend, charge it to my CC, and don't go on that trip, can I rebook the total value on another ticket for one person only that maybe is more expensive.

In other words does the credit get divided - half per person and future reservations must be made in both of those names?

Example:
HOU to MSY for 2 people =$263.00 for both on one confirmation #.
Cancel trip.
Apply credit for 1 person HOU to LAS which costs $270

Would this work or would I just be able to apply 131.50 to the second more expensive trip for 1 person?