You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am William Jackson, want to alter my recent reservation due to some emergency. Please help me out with that.

ASSISTANT: Sure, please wait a minute.

USER: Ok, take your time.

ASSISTANT: Sorry William, there is no active reservation found under your name in our records.

USER: It's ok, thank you for your help.

ASSISTANT: Most welcome.