You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I want to change my existing reservation, due to sudden change in climate at my source. Can you please help me?

ASSISTANT: Sure, I will help you with that.

USER: Thanks for accepting my request.

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

USER: Sure, my name is Jeffrey Roberts.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

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: That's Ok, thanks for your assistance.

ASSISTANT: Thank you for choosing us.