You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you at this moment?

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

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Can I have your name please to check your reservation status?

USER: My name is Sarah Clark.

ASSISTANT: Ok, please wait a moment to check your reservation.

USER: Sure, take your time.

ASSISTANT: Sorry Sarah Clark, no reservation has found under your name to change.

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

ASSISTANT: Thank you for choosing us, have a great day.