You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I have to attend an important meeting, so I am unable to catch the flight. Can you please change the travelling dates of my previous ticket?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Can I know your name for checking your past reservation status?

USER: Ok, my name is Charles Hernandez.

ASSISTANT: Ok Charles, please wait for a minute.

USER: Ok, take your time.

ASSISTANT: Sorry for the inconvenience, there is no reservation on your name in our database.

USER: It's ok, thank you for spending your valuable time.

ASSISTANT: Thank you for contacting us.