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The way these certs work is that once used they're gone. If you carefully look at the price paid as listed in your PNR you'll see the the base fare is $250 less than was listed when you made the reservation. So when they refund you the ticket value it will be for this amount. You may call the customer relations and plead with them to issue you a new cert but prepare yourself for a disappointment. The only time I was successful was when I had to cancel due to UA's fault.