You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I would like to shift my planned dates to some other dates, please help me in changing my existing reservation.

ASSISTANT: Yes, can you tell me your name?

USER: My name is Helen Walker.

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

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

ASSISTANT: Thank you for reaching us.