You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Joshua Clark.

ASSISTANT: OK Joshua, how may I help you?

USER: I have already done with my flight booking, but now due to an urgent business meeting I would like to change my reservation.

ASSISTANT: Sure, I can help you. Wait a moment to check the details.

USER: OK.

ASSISTANT: Sorry Clark, we could not find any reservation ticket on your name.

USER: It's OK. Thank you for your information.

ASSISTANT: Thank you for reaching us.