I'm not an expert by any means, but it only seems logical that they would allow you to upgrade back to your original class of service. You accepted a voluntary downgrade to D because, at the time of booking, A class was not available; now that there is availability in A, you should be put back into A. Sounds like it might require jumping through some hoops (i.e. getting ticket re-issued), but I just don't see why it should not be free.

FewMiles..

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