You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Can you please help me to change my existing reservation as my meeting with the client got postponed?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Please share me your name to check your details.

USER: My name is David Carter.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: David Carter, sorry to inform you that there is no reservation found on your name to proceed further.

USER: No problem, thank you for your time.

ASSISTANT: Thank you for choosing us.