I once made a phone reservation for Hertz car rental for a friend when my DSL went out. He needed to get home within a couple of days from JAX just before the superbowl. I knew that Hertz had a decent weekend rate. I had him take a cab to the airport and using an old receipt, I gave the phone rep my CDP and coupon codes. He paid approx $25 total for a 2 day compact car rental. I was able to change his flights with only a change fee charged.