Thanks to everyone for chiming in here. I will call SPG again as I cant seem to get the App to allow me to do this. I would rather do this with SPG than have to call the property as in my experience, the front desk people try very hard to not mess with reservations (unless you are there "live" at the property).... but will of course do that as a last resort.

I will report back after I try again.

Thanks !!