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

ASSISTANT: Hello, how may I assist you?

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

ASSISTANT: Sure, please wait a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: Not an issue. Thank you for your information.

ASSISTANT: Thank you for opting us.