You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Timothy Clark here.

ASSISTANT: How may I assist you?

USER: Can you change my flight ticket reservation?

ASSISTANT: Give me a moment please.

USER: Ok.

ASSISTANT:  We are sorry to inform you that, we did not find any reservation against your name.

USER: That is not a problem.

ASSISTANT: My pleasure.

USER: Thank you.

ASSISTANT: Welcome.