Complaint sub-issue: Credit card company isn't resolving a dispute about a purchase on your statement

I booked two flight tickets with an online travel agent, XXXX , XXXX in the amount of {$1500.00}. Initially, I made duplicate bookings for the exact same itinerary. Due to the travel agent 's website issues, I was not able to get confirmed tickets and there was no US phone # for me to call and they failed to respond to my email inquiry. All I got was the travel agent 's order #. The order could not be found in both the airline websites and the travel agent 's website. I worried about online scam. I contacted Citibank to express my concerns. Citibank put the transaction under fraud dispute and advised me to rebook my tickets. I rebooked the tickets with XXXX on the same date. It was 8 days after the booking with XXXX, they finally confirmed tickets. Citibank chargeback the transaction to XXXX. The travel agent got in touch with me to inquire about the chargeback they received from Citi. I responded to them and provided Citibank an update regarding the communication I had with XXXX. Citiback told me that they could not investigate the case because I got in touch with the XXXX. Citibank stated that they would close the case and reverse it to a general dispute. On XX/XX/2020, Citibank closed the dispute and reposted the transaction to my account. They nerve reverse the dispute. On XX/XX/2020, XXXX canceled my reservation at the very last minute without notification and my consent. I had to rebook another flight tickets to get my destination. I requested a full refund from XXXX, they refused to provide me a refund. They stated that Citibank is in favor with them. I called Citibank to request a dispute of the charge. Citibanki rep refused to reopen the dispute. The rep stated that the charge was initially dispute under fraud, once a charge is under fraud investigation, Citi would not reopen the dispute. I told the representative, under the Fair Credit Billing Act, I have the right to dispute this charge ; however, the rep told me that I have to deal with XXXX  to get my refund. They cant help. On XX/XX/2020, I went to a Citi branch to seek for help. The branch rep called Citi Credit Card for me and we were told that they could not reopen the case until 1st week of XXXX. On XX/XX/2020, I went back to the same branch and the rep called Citi Credit Card, I was told that I needed to submit a written letter and supporting documents for the dispute. On XX/XX/2020, I submitted my dispute via email as well to the Citi branch rep for him to escalate my request. Citibank declined my disputed on XX/XX/2020. Citi stating that the information they had was not enough to support my claim and resolve the dispute in my favor. The transaction will not be removed from my account. There was no explanation or supporting documents for the decline. Citi did not contact me to ask questions or request any documents other than a final letter notifying me that the charge stands. I do not know Citis investigation/review standard. All I know is that XXXX did not provide me service. They cancelled my flight tickets on XX/XX/2020 and the merchant stated that Citi is in favor of them. I did not want to have an outstanding balance, I made a full payment to Citi for XXXX transaction on XX/XX/2020. I have attached a detail letter and the supporting documents for your review and recourse to me as at this point, I feel victimized in this process. Please assist in providing me the directions needed to help as I have no other options to get closure currently. Please contact me if you any additional information.