I have a couple of ticket credits for $300 each. have some flights of $100 each coming up and would like to use, but of course don;t want to lose the residual value. Is there a way to deposit the ticket value into my wallet so that I can the precise amounts I need? Separate question: If I use the $300 towards a 2019 ticket of $400, but then need to cancel that new $400 ticket, can the $400 then go to my wallet?