Question: Airline credit and change fee question. Help!?

By | August 10, 2018
I recently bought a departure and return ticket from NY To Tampa and I had to cancel my flights. I got a credit of 239 for one ticket and the other I got a credit of 291. Now both tickets are with different airlines so the change fee is 150 for one and 200 for the other. How do I make the most of my credit now for when I want to book another flight (any destination). I just want to make this as cost efficient as possible. Please help airline gurus!