Quite slow going in this part of the board...
I just realised that I'm sitting on a number of u/g vouchers with limited shelf life and they'll keep coming with the hopefully soon-to-be-reached Plat level.
So I called AY to change a C award paid fully with points to an Y award + u/g voucher. It took a full 3 minutes to have it done and the points to be redeposited to my account. No need to re-issue, as the ticket itself was not changed, only the payment method.
^