I have made a reservation but did not notice I could not cancel except the next day. Being this is unusual for us rewards members, do you think I could change it for another date? I believe it might have been charged on my card in file, but haven´t checked.
It's actually quite common. Almost all properties include a prepay rate now if booked more than a week (or so) in advance. What happened when you called the silver line? I have had success when I needed to cancel past check in deadline due to cancelled flights etc. I can guarantee you this. You WILL have to pay if you don't ask for help. Your best odds are if you are simply moving the reservation and not asking for a refund.