You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Melissa Jones here.

ASSISTANT: Melissa, how can I aid you?

USER: Can you change my flight ticket reservation?

ASSISTANT: Sure, please give me a minute to check your ticket status.

USER: Ok.

ASSISTANT: Sorry, no reservation is found.

USER: May be I have not booked the flight ticket yet. Thanks for your information.

ASSISTANT: Thank you for reaching us.