Yes, if you've booked a new reservation at a rate we found for you, you'll want to cancel any old reservations you may have booked that you won't be using.
If you've booked a rental somewhere else and then submit it for price tracking, we'll watch the rate and send you an email if a lower price comes along. If you click the link in our email and book a new reservation, please note this does not automatically cancel your old, more expensive reservation. You'll need to contact whomever you originally booked the reservation to cancel it.
Although there's no penalty to cancel or no-show most rental car reservations, we do recommend that you cancel any reservations you don't intend to use at least a couple of days before you pick up your car. This is both to prevent any confusion at the rental counter about which reservation you're picking up (so you don't accidentally rent at your old, higher rate) and to help the rental companies plan their availability better.