You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I want to some changes in my existing reservation. can you help me for that?

ASSISTANT: Sure, may I know your name?

USER: My name is Sandra Lee.

ASSISTANT: Please give me a moment to check your ticket status. Sorry Sandra Lee, no reservation is available by your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for reaching us.

USER: Welcome.