Good car, unfortunate administrative error from Alamo.

When I received the car from BNE airport, I did not received a full tank. As I only noticed after I drove out of the Airport, I took a picture of the fuel gauge and did not drive back. When returning the car, I told the staff at the airport about the issue, and showed them the photo. They verified the time of the photo taken, and agreed that I will not be charged for fuel. In fact, I returned the car with more fuel than I received. The staff even asked me to send the photo to for them to forward to the management. but later in the day I receive a RA stating I will be charged for refueling of 15L. I tried to email Alamo through their website to the BNE office, but there is no confirmation that the email was received, or any respond from them in any way.