Dollar Rental Cars

When I arrived to pick up my rental car at the airport i asked if they had any military discounts. The man behind the counter said he could give me  a free upgrade with a military ID.  I signed the agreeement on an electronic screen that was up high on the counter and was not very readable. When I got to my destination and looked at printed agreement,I noticed they charged me for $20 a day for a total of $140 for the upgrade. I called customer service and they told me they couldnt change it over the phone and I should see the manager when I returned the car. Unfortunately when I returned the car there was a very long wait at baggage heck and security so we did not ave time to wait in line at rental desk. later  I called customer service line at Dollar and they refused to credit me any money because i signed the agreement to pay $140 for the upgrade. 
What is even worse is the fact they said the nissan maxima was a full size car and my orig rental was mid size. the Maxima really only seats 4 because the middle seat in back is not a full seat.  It was definitely not worth $20 more a day from the other car we would have received. 
In addition the car smelled. It was the second car they brought to us so we did not feel like waiting for a third car. The first car  that we loaded our suitcases in did not have keys so they had to go get another car.
There were several fees and taxes listed on the agreement that they never explained and the fees  were much more than $80 listed on the reservation.
I will NEVER use Dollar Rental Car again.