You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How exactly I can serve you the best today?

USER: I would like to change my existing reservation, can you help me in doing that?

ASSISTANT:  Sure, I am here to assist you.

USER: Thank you.

ASSISTANT: Let me know your name to check your reservation?

USER: I am Elizabeth Evans.

ASSISTANT: Ok, please wait a moment.

USER: Sure, take your time.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your ticket, but could not find any reservation with your name.

USER: Ok, no issues. Thank you for checking.

ASSISTANT: Thank you for choosing us.