Unless it has changed recently, you do not have to cancel the reservation but can go to modify the reservation. you can select the contracts to use and any banked or borrowed points are used before any other points. I know several years ago , I had reservation for CCV made at 11 months , I then ended up buying another contract with banked points. I modified the reservation and selected the contracts to use including the new one with banked points. No problems. One can do this and at the end you can look at which points used. If not correct ,can cancel the modification before leaving the page.
One can also call MS.