Yeah, I've done that over the last 2 years. It's time consuming, and sometimes you have to be very persistent with the agent. They will often give you misinformation that you can do it on their website. Because I'm buying a new Frontier ticket every month or two, I generally find it less hassle to just take the credit. If I flew them less often, or had a large purchase I was cancelling (my typical Frontier ticket is probably 30 bucks) I'd be more persistent in having them give me the money I'm entitled to.