Alamo car rental

I rented an auto from Alamo through Auto Slash for 7 days use in Hawaii beginning 12/30/18 and returned 1/5/19. I originally agreed to rent an intermediate vehicle at a cost of $396 paid with my Bank of America American Express card. At the Alamo rental office in Kona, I was asked if I would like to upgrade the vehilce to a mid-sized non-4wheel drive Jeep Cherokee. I was told that there would be an additional charge of $10.00. I agreed to the upgrade. I understood that Auto Slash's terms and conditions state that I was responsible for the cost of any upgrades. Later, when I had returned the vehicle, Alamo ran my American Express credit card for an additional $405.01, including taxes. Alamo charged me the full $49.99 per day rate for the Jeep Cherokee on top of the $396 already paid. Thus, I was charged over $900, including taxes, for 7 days rental of a car that rents for $49.99 per day. I have contacted Alamo customer service by phone on two occasions about this dispute. Each time I called, the Alamo customer service representative told me that they would investigate the matter and contact me by phone. Neither customer service person could offer any explanation for why I was charged the full rental rate on top of the $396 rather than for just the cost of the upgrade. I have never received a return call. I believe the Alamo Rental Agreement # is ***. I was given Reference # *** when I contacted Alamo customer service.

I made a car reservation (CN#*** for car pick up May 25) on alamo.com on April 19th, 2019 around 11 pm for the amount of $105.27. Around 11:30pm I found a better deal on another website so I canceled this reservation. However, I was charged $50 for cancellation fee, which I think it was outrageous and unreasonable. If I canceled within 24 hours, I should entitle to full refund. Let alone I canceled within 30 mins. I called the alamo center and was told this is their policy, I don't think this policy is unfair to the customers and it's a total robbery.

Reserved a rental through Costco, used the self serve KIOSK. I declined insurance, damage waiver, and the refueling option.
Went to pick up the vehicle, I was given a free upgrade. As we were exiting and the agent was signing off on our contract, he told us to not refill the tank when we returned the vehicle and stamped my contract folder with a large 'Prepaid Fuel Reminder Do Not Fill' stamp in red and said something about "we will take care of your gas for you, don't forget! Don't refill the tank!" I guess this was part of the upgrade? Is this guy in a good mood?
Upon return of the vehicle, we had a little more than a quarter tank left and when the agent taking the vehicle from us gave us a reciept, I saw that we were charged $62.20 for a 'FSO' which I researched and found to be a Fuel Service Option.
I called Alamo and spoke with Patrick who took my information and gave me a reference number. He let me know that my inquiry would be given to the Alamo manager at Lihue and she would get back to me. She has yet to call me back.
I called back 5 days later and spoke with Drew. I told him it was confusing when my contract was stamped with a 'Do Not Refill' stamp when I had declined the refueling option, I said,"If my contract wasn't stamped with 'Do Not Refill' I would have refilled the tank, and I had refilled the tank during the rental once already". Drew suddenly became short and snippy with me and said, "It doesn't matter what was stamped on your contract, you are responsible for refilling the tank." He offered me an $8 refund since he claims the tank was 2/8ths full. I indicated that I really wanted to speak with the manager at Lihue to try to sort out the confusion, Drew said he saw my ticket in the system and basically told me I wasn't going to get anywhere with that and I should just take the $8.
I rent vehicles regularly and have never run into a rental agreement as confusing or as deceptive as this one.