You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I would like to change my existing reservation. Could you please help me out in changing reservation?

ASSISTANT: Yes, I can help you. Can you share me your name for checking?

USER: Myself Margaret Nelson.

ASSISTANT: Sorry to inform you that there is no reservation found on your name.

USER: Not a problem, thank you for checking. Thank you for helping.

ASSISTANT: Thank you for contacting us.