So can I clarify the issue here?
- You booked a pre-paid rate.
- You want to extend the stay for an extra night, but find the rate to be too high
- You want the hotel to extend your existing booking to a slightly higher rate, and therefore, include the extra night
- The hotel took its time to respond and when it did, it wasn't the answer you wanted
Are you annoyed because:
a) The hotel took its time to answer and as a result, you've spent your own points to cover the extra night, or,
b) The hotel didn't do what you want, or,
c) Both a) and b)
To be perfectly frank, the hotel is under no obligation to change your existing booking even if it's to a higher rate to cover the extra night. You may see it as a compromise on your part, but if I was the hotel, I won't see it that way.
My understanding of a pre-paid booking (regardless of whether the card is charged or not) is that it can't be changed or cancelled. You want the hotel to extend the booking, that's a change. You need to make a separate booking for one night, and unfortunately in your case, it works out to be either $499 or $719.
Personally, if you want the hotel to do what you want, I feel it's being unreasonable. The only case you may have is the slowness of its response, even then, it isn't a big deal.
Also, something doesn't add up. How can the hotel still allow you to book 3 nights, but not one? If it claims it's full for that 3rd night, it shouldn't allow you to book 3 nights.
Lastly, if it's all company expense anyway, why didn't just book that extra night regardless of rate? I'd just book that night at $499 (assuming that high rate is a rate you can cancel), and hope with an outside chance the hotel would do what you want. If it did do what you wanted, cancel that high rate then.