You say you banked them? So they moved apparently from the current year 2018 into the 2019 use year? When you cancel a reservation with more than 30 days out, they do not going Into Holding. They will go back into whatever status they had before you used them on the reservation. So they will go back into the same banked status that they had before. They will remain in the Use year where they were, whether you use them or not. So you do not need to re-bank them. They automatically go into the bank under the same conditions as they would have been had you not used them at all.
However I agree with Kat4Disney. The banked points will not be used automatically on your March reservation. The points you used to schedule the March reservation are the points that will remain on that reservation. However, you can change this by calling them and asking them to do it. Which you Should do relatively soon. The DVC reservations department agents can do it. But the only way you could do it by yourself would be to cancel the March reservation and then rebook it using the banked points. Of course you might lose the reservation in the process, since once you cancel it, whoever has a waitlist request with that date, will automatically receive it. If there is anyone who has waitlisted it.
