Originally Posted by Happy

In majority of the cases, a paid reward stay when canceled, the points immediately return to the account as reflected in the balance, for as bad as Marriott IT has been - the refund of points since late last year / early this year, has not had any glitch from own experiences as well as hardly any more negative DPs in this forum - so I think you can cancel the existing bookings and immediately rebook the lower cost one - because you would have seen there is availability with the lower cost to begin with - cancelling a higher cost booking should not reduce the availability, but add to it - in theory any way.