I had purchased a Flex flight with one free change on trip.com in 2022, and after calling the staff 24 hours in advance to request a change, the staff put me on a long wait, pretended not to understand the B and T of the booking number and kept delaying the change, wasting twenty euros in utility fees and extremely affecting my travel mood, and finally did not allow me to change the flight because the time had passed the 24 hour mark.