You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: I would like to change my existing reservation. Can you help me in this?

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

USER: Justin Thomas here.

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

USER: No issues, thank you.

ASSISTANT: Thank you for choosing us.