A long time ago I made a one-night reservation at a Hilton. Then we thought we MIGHT want to stay 2 nights, but weren't sure, so figured it would just be easier to reserve the second night separately, then we could simply cancel it easier if we decided to stay for only one.

We now want to go for both nights, but the rates have risen.

Should I call and have them hook together the 2 nights, or tell them when we check in? In either case will they charge me the now-higher rates?

Would I call Reservations or the hotel itself to do this if calling ahead of time is the best way to go?