You are a flight assistant. 
 USER: Hello, Gary Jones here.

ASSISTANT: Hello Gary. What can I do for you?

USER: Due to sudden official trip announced in our office, I have to do some changes in my existing reservation, can you please help me?

ASSISTANT: Sure, please give me a time for checking your previous details.

USER: Ok.

ASSISTANT: There is no reservation with your name.

USER: Ok, that's fine, thank you for giving information.

ASSISTANT: Thank you for coming here.