The rental car was nice and everything went as pla...

The rental car was nice and everything went as planned. I had an issue when I returned the car. I had an Enterprise Gift Card I wanted to use towards the rental fee and I was told I was unable to use the Enterprise Gift Card when I returned the vehicle which was highly upsetting as it would of covered a good portion of the charges. She said I needed to enter it when I made the reservation however there was no payment information or gift card field available when I reserved the vehicle through the Enterprise App.