You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Mark Roberts. Due to some personal work I would like to change my recent reservation, can you help me with this?

ASSISTANT: Please wait a while.

USER: Sure, take your own time.

ASSISTANT: Sorry to say, there is no reservation on your name in our database.

USER: That's fine, not a issue.

ASSISTANT: Thank you for choosing us.

USER: Thanks for your help and information.