You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,.

USER: I am Shirley Walker.

ASSISTANT: How can I assist you?

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

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: I regret no reservation found by name Shirley Walker.

USER: No problem, thank you.

ASSISTANT: Thanks.