I think the issue may have been that although the change was made, the etkt wasn’t reissued and so therefore the booking was auto cancelled.

so a back office screw up and then of course you faced the usual lack of empowerment from a QR phone agent.

frustrating as hell doesn’t cover it. It’s unacceptable but I agree that it’s unlikely an overbooking situation that caused it, let alone DXB station deciding to cancel/offload you to balance their numbers.