Several weeks ago, I booked a reservation at the Park Hyatt Los Angeles for three nights, using the Hyatt Web site.

I've just learned that I need to arrive in Los Angeles a day earlier, meaning that I'd like to extend my stay by one day. Fortunately, the hotel has availability for the "extra" night.

Ordinarily, I'd simply:

• Book a new reservation for four nights.
• Cancel my old reservation.

However, I just discovered that the hotel is full for one of my original three nights.

Also, the rate is now higher than it was when I confirmed my reservation.

So, should I book a separate reservation for the extra night (and then explain the situation when I check in)?

Or should I call and ask about modifying the existing reservation? If so, should I call the hotel or Reservations?

Thanks for any advice.