I am on a redemption booking: LAX-LHR-MUC in J. F became available LAX-LHR. Very polite HK agent told me I could not use avios to upgrade into F because that segment was married with the LHR-MUC segment, for which redemptions were no longer available. She could not do the upgrade without cancelling the existing reservation and since there was nothing to book into, no upgrade. I had no tools at my disposal to argue with her, and she really was very polite.

So the question, was she right or was she wrong?