Refer to the email that was sent when you made the booking! That is the price and it is GUARANTEED!

I have found lately (over the past few months) that existing bookings show different prices depending on the offers/pricing going at the time

I have had a few reservations recently change by $60 for a 2 day booking when I went to log-in to check dates booked etc..

Was booked for $170, now $110 as there is a cheaper rate running for the weekend.

Never experienced a rate change before on existing bookings until now. My guess is another system glitch that just shows the CURRENT pricing on EXISTING bookings.

The final response Hertz gave you is the best advice.

Take the printout to the counter/check your contract before you leave the lot and get them to fix the price there.

They can easily add a credit/change the price at the counter. Over the phone it seems impossible like you have said.