I recently received my Hilton credit card and with it came several Hilton certificates. One of them was for a room upgrade.

When reserving a room at the SF Hilton via the HHonors phone line I was told that the cert is only good for one night of stay and that I would need two for my two night stay.

Nothing in the rules on the cert indicate that it is good for one night only. Was the HHonors person correct? By way of comparision, what are the rules for the books of upgrades one can buy from Hilton?

Thank you