Originally Posted by
miamigrad
The whole award will have to be cancelled, the miles re-instated, and a new award issued.
All of the miles will have to come from a single account.
And, while they seem to waive fees for "upgrading" awards to higher cabins, it is quite possible that they won't do it in this case where it is a redeposit to one account and a draw from another.
Cheers.