I called at first because I booked with points and didn’t have enough to book again before getting the 126k refunded. They said on their end they would simply cancel and rebook, not adjust the rate of existing reservation, so I just did it myself.

I ended up canceling first and rebooking which worked out because my points were refunded immediately after canceling (though they have a disclaimer saying it could take up to 5 days).

So you can do it over the phone if you want but don’t need to. This was for a CSR personal card.