You are a flight assistant. 
 USER: Hello. I am Steven Smith.

ASSISTANT: Hello, how may I support you?

USER: I want to change my existing reservation due to postponed of my journey dates. Can you please help me with that?

ASSISTANT: Sure.

USER: Thank you.

ASSISTANT: Give me a minute.

USER: Sure.

ASSISTANT: Thanks for being waiting.

USER: OK.

ASSISTANT: We didn't found any reservation by this name.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for reaching us.