You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Jonathan Lee.

ASSISTANT: How can I oblige you today?

USER: I want to change my existing reservation due to postpone of my client meeting, can you help me in change reservation?

ASSISTANT: Please give me a moment, let me check your reservation and revert to you.

USER: Ok.

ASSISTANT: We did not find any reservation on your given name in our data.

USER: Ok, no problem. Thank you for your help.

ASSISTANT: Thank you for choosing us.