bicker said:
Any time you change a car rental reservation, unless you paid a deposit or did a pre-pay, you're subject to the prevailing rates, and therefore lose any rates you might of had previously.
Interestingly enough, Brian, this seems to not be the case with National. Depending on what sort of changes one is making, it seems that the previous rate will still be the one that holds for the reservation.
I know, for instance, that one can apply a coupon or a discount code and still keep the original base rate. I just did that myself last week. Similarly, one can *shorten* a reservation and keep the previous rate.
*Extending* a reservation seems to be unclear. As an experiment, I tried adding a day to a reservation I made when prices were much lower than they are now. It looks like the original rate still applies for the original rental period, but the new higher rate was applied to the additional day. (I'm not certain this is what happened, but the rate is far lower than it would have been for a new reservatin at currently available rates.)
This is still a much better situation than National had a few years ago. Because of quirks in their web site programming, it was not uncommon for the rate to change on a reservation simply as a result of calling it up to reconfirm its status. (Ain't the web a wonderful place?)
Having said all this, I can't explain what happened to our original poster. My suggestions would be first to just try it again, and see if it was a hiccup in the reservation computer, or, second, call the National 800 number and try the change through an agent.
I think there may also be a separate number for web support - that would be the number to call first, since often phone agents and online reservations have different rates.
(Added after the fact) - There's a place on the web site where you can send questions/inquiries without having to go through the phone. Click on the "contacts" tab, and then on the link to "reservations department".