Hello, To change his ticket, my cousin went to the [Air China Sales Office in Ulaanbaatar](https://rightcheckin.com/airlines/air-china-city-sales-office-in-ulaanbaatar/). The staff was really helpful and gave an in-depth account of the process. However, the large number of customers resulted in a lengthy wait for her. Both the agents and the agency were professional and well-run. Even though there was a delay, she was ultimately happy with the service.