Since Hertz never responded to my email I chatted with a rep on Live Help instead.

Basically your Hertz account will reflect the new lower rate on your reservation, but if you don't call the 1-800 number to "lock it in", it goes back to your original rate once the lower rate is no longer available.

Yet there will be nothing on the website to inform you of this seemingly deceitful practice. So let this be a warning to all: don't take it for granted, always cancel and rebook even if the lower rate is now reflected in your reservation.

I still feel pretty incredulous about the whole thing. What shady business practice. I might just cancel my reservation and take my business elsewhere even if it means I'd have to pay a higher rate.