You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Sure, I will help you with that.

USER: Sure.

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

USER: Stephanie Martin.

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: Ok, no problem. Thanks for your information.

ASSISTANT: Thank you for choosing us.