Enterprise Car Rental --- 6900 TOWER RD, DENVER, CO 80249-6333 Enterprise Car Rental charges one extra day for my car rental DENVER Colorado

I had a trip to Denver, Colorado during July of 2013. Before the trip we booked a car rental thru Enterprise. We booked our flights to fly to Denver on July 10th and to come back to Philadelphia on the night of July 20th, 2013 which was a Saturday. We picked our car around noon time on July the 10th at this location: HOLIDAY INN TOWER, 6900 TOWER RD, DENVER, CO 80249-6333, Tel.: (303) 371-6850.  When we picked up the car, we asked the rental agents what we should do when we return the car on July 20th when nobody is available at the office, since it was a Saturday and they only operate the business until noon of Saturday, and the office will be closed on Sunday. What we were told was that we can simply give the key to the front desk folks at Holiday Inn (the Enterprise office is actually in the lobby area of the hotel). So we did not think too much at that time. On the night of July 20th around 9 pm, we drove the car back to the hotel, we talked to the folks at Holiday Inn, they asked us to sign in the notebook which recorded the date and time for the return car, we then gave them the key. But after we got back home and received the bill from Enterprise, we were surprized to see that they were using July 22nd as the return date, I guess that was probably the time they got the key from the Holiday Inn folks. So I called immediately, the lady I talked to actually realized that it was a mistake and told us that they were going to issue me a credit for that one day. But after so many months I did not see that from my credit card bill. Interestingly we went together with some friends (same flight to go and come back, same rental duration with the same company), and they were also charged for one day extra! Although in their care after numerous tries, they were able to get the credit back, but I did not. So at this point, I don't know where to contact, this is probably the best palce for Enterprise headquarter to realize that unhappy customers like me are out their. I can provide more details such as my itinery ticket, my friends' proof of our car return time etc. I hope Holiday Inn kept the log of car returns on that day (July 20th, 2013).