You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: I want to change my destination airport code in my existing reservation, can you please help me out?

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

USER: Sure, my name is John Clark.

ASSISTANT: Ok, please wait a moment.

USER: Ok, take your time.

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

USER: It's ok, thank you for the information.

ASSISTANT: Thank you for choosing us.