You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I'm Karen Davis.

ASSISTANT: How can I assist you today?

USER: I had planned to meet my friend, but it was postponed.Can you change my recent reservation?

ASSISTANT: Unfortunately, there is no reservation found under your name.

USER: That's really sad. Thank you for your help.

ASSISTANT: Welcome, have a great day.