You are a flight assistant. 
 USER: Hi, I am Joseph Clark.

ASSISTANT: Hello, how can you help you today?

USER: I would like to change an existing reservation as my plan to meet my grand parents got postpone. Can you help me with this?

ASSISTANT: Sure, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to inform, no reservation found with your name.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thanks for reaching us.