Product: Debt collection

My company uses American Express Global Business Travel ( GBT ) to handle our business trips. On XX/XX/XXXX I made a reservation for a one week stay in XXXX XXXX for business travel. I used the website to make the reservation. It was very difficult to find any hotels available so I ended up choosing XXXX XXXX XXXX as it was practically the only one available that week even though they were more expensive than I had a travel budget for. The trip was planned for XX/XX/XXXX so I made the reservation as soon as I had my management approval. After reviewing the total cost of the hotel with my manager, we realized it was way over the budget and it would be best to find a cheaper one. I tried once again, but this time I called American Express GBT and spoke with an agent on XX/XX/XXXX. I explained the situation and told her I had found a cheaper hotel where the rest of my team was staying at. The agent made some calls and assured me that XXXX XXXX XXXX allowed her to make the cancellation and there would be no penalty. I even had her confirm what she said because I wanted to make absolutely sure I would not get charged. Only then did I tell her to proceed making the reservation for the new hotel. The trip was confirmed and I received the invoice and email confirmation for the hotel stay. 
After my return from XXXX, I noticed that I had 2 charges on my credit card, one from the hotel I stayed at and the other from XXXX. I thought surely it was a mistake and that American Express would fix the issue. 
I submitted an inquiry on XX/XX/XXXX with American Express GBT and created a case. I received a phone call from a representative and she said she would work with XXXX to find a resolution. She was able to confirm that there was a cancellation number that XXXX XXXX system generated thereby proving that the cancellation was confirmed without any issues. She said they would get back to me with the response from XXXX. 
After several back and forth conversations, I got an email on XX/XX/XXXX from American Express GBT indicating that XXXX had rejected the refund due to their policy. And as far as American Express GBT, they also added that they could not give a refund for a vendor error and that my case was closed. 
I had paid my American Express bill of {$3400.00} out of my own funds because I wanted to avoid penalty fees and was confident that I would get a refund due to the mistake that was made by either the system, XXXX or American Express GBT. But instead I was being told that I had to pay for the system mistake. 
I was very disappointed by the way GBT had handled my case so I shared what had happened with other co-workers. I was told that something similar had happened to another teammate. He advised me to open another case and insist so I did. I made several more phone calls each time having to speak to different GBT representatives who continued to tell me to wait and that I'd hear back from them, but I never would. So I continued to call back even if I had to repeat the same story over and over again. I even managed to escalate to some supervisor who assured me they were doing everything possible to resolve this matter. I was also told that even if XXXX did not refund me, GBT would be able to refund me the money due to the mistake. After ongoing calls, I finally got a final response from GBT on XX/XX/XXXX via an auto-generated email sending me the exact email that was sent to me in XXXX. This was severely disappointing since I had been assured by several representatives that my case had been escalated and they had contacted XXXX again and that GBT would pursue the refund, etc. etc. But when I got the email with the exact response that I had gotten in XXXX it confirmed that the last few months of my calls and acknowledgements that my case had been escalated were completely false. It seems nothing further was done and the default answer was that XXXX refused to give the refund and that GBT was not responsible. Therefore I the customer get penalized for a system mistake and for believing the GBT agent 's assurance during my phone conversation on XX/XX/XXXX that I would not be penalized for the cancellation. This mistake has cost me {$3400.00} and several months of time wasted in believing that someone was actually trying to help get me a refund.